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L f&Cj 4- 




This copy was picked up in 
a second-hand "book stall in 
London 1>y Mr. Henry Peter 
Shopneck in late 1931 or 
early 1932 - and given "by 
him to Dr. Little. 



THE 



CHEMISTRY 



PAPEK-MAKING 



TOGETHER WITH THE 



PEINCIPLES OF GENEKAL CHEMISTET 



A HANDBOOK FOR THE STUDENT AND MANUFACTURER 




BY 



R. B. GRIFFIN and A. D. LITTLE 



NEW YORK 
HOWARD LOCKWOOD & CO. 

1894 




AV 



■ ^' 














cA$- 



-\iM 



Entered according to Act of Congress, in the year 1894, by Howard Lockwood & Co. 
in the office of the Librarian of Congress at Washington. 



PREFACE. 



A considerable part of this book has been devoted to the 
elementary facts and principles of general chemistry and to proc- 
esses of chemical analysis which are, in the main, well known, in 
the hope that the strictly technical portion might thus be ren- 
dered more available to the large body of paper-makers whose 
knowledge of the science is limited. For this reason the Intro- 
duction treats briefly of chemical theory, while Part I. contains 
a short account of the different elements and a reference to their 
more important compounds. In Chapter VIII. the various 
analytical processes which are employed in the examination of 
paper-making materials are given at some length. 

Among the numerous authorities consulted special mention 
should be made of Groodale's "Vegetable Physiology," Sargeant's 
"Report on the Forest Trees of North America," Schubert's 
"Die Cellulosef abrikation, " the very complete reports of the 
State Board of Health of Massachusetts in connection with the 
subject of water, and files of "The Paper Trade Journal" 
and Hofmann's Papier- Zeitumg '. The excellent plate of fibres 
is from the valuable little book by Dr. W. Herzberg entitled 
' ' Papier-Priif ung, " in which also may be found many of the 
facts relating to the German methods of paper-testing. The 
numerous papers and reports of Cross and Bevan on cellulose, 
fibres, and the processes of paper-making have been freely drawn 
upon. 



PRE IT ACE 



This opportunity is taken to thank collectively the many 
friends in the paper trade who have kindly contributed the 
results of their experience and permitted the publication of 
analyses made in our laboratory for them. Valuable assistance 
has also been received in various ways from Messrs. A. Wendler, 
E. C. Albree, J. L. Hecht, George T. Cooke and Dr. Frederick 
Fox. 

The death of my friend and partner deprived me of his 
co-operation when the book was only partially completed, and 
has at many points obliged me to forego that fullness of treat- 
ment which his aid would have rendered easy. 

A. D. LITTLE. 

Boston, August, 1894. 



CONTENTS. 



PAGE 

Introduction — Principles of Chemical Theory ........... 3 



PART I. 

general chemistry. 

The Non-Metallic Elements 25 

The Metallic Elements ...'....... 62 

PART II. 

the chemistry of paper-making. 

CHAP. 

I. Cellulose . 103 

II. Fibres 117 

III. Process for Isolating Cellulose ...... ... 151 

Rag Boiling 151 

Treatment of Picker Seed and Picker Waste 158 

Esparto 157 

Straw 158 

Manufacture of Wood Fibre:—- 

The Soda Process 161 

The Sulphate Process . 178 

The Sulphite Process 179 

Theory 182 

History 185 

Preparing Wood 188 

Liquor-making 190 

Digesters and Linings . 232 

Boiling 250 

Recovery of Gas 261 

The Waste Liquor .............. 270 

v 



vi CONTENTS. 



IV Bleaching 275 

V. Sizing and Loading 301 

VI. Coloring 320 

VII. Water 329 

VIII. Chemical Analysis 348 

IX. Paper-testing 420 

X. Electrolytic Processes .............. 452 



Appendix ....................... 463 

Index ................... 503 



THE 
CHEMISTRY OF PAPER-MAKING. 



THE 
CHEMISTRY OF PAPER-MAKING. 

INTRODUCTION. 

Physical and Chemical Change. — The action of force upon 
matter gives rise to changes which are called physical or chemical, 
according as the identity of the substance acted upon is preserved 
or lost. In grinding wood, each particle of the pulp remains a bit 
of wood ; in beating stock or forming a sheet of paper, the identity 
of the cellulose is not affected. Rosin may be melted or broken 
down to powder, but its character as rosin remains the same. Iron 
may be forged, rolled, filed to dust, or drawn to wire along which 
an electric current passes, but in each case the product of the 
process is iron. All of these changes are non-essential ones so far 
as the identity of the substances is concerned. The composition 
of the substances has been unaffected and the changes are physical 
ones. 

If rags are boiled for some hours with acid, glucose is formed. 
Rosin is heated with soda, and a size which is different from either 
is prepared. Iron rusts in the air or burns in the forge or dissolves 
in acid, and the products would never be confounded with the 
metal. These are chemical changes, the identity of the materials 
involved in them has been lost, and new and different sub- 
stances have appeared. The changes have affected the ultimate 
constitution of the substances, and they are no longer what they 
were. It is with such changes that the science of Chemistry has 
to deal. 

Conservation of Energy and Matter. — Chemistry, in the 
modern sense, began with the recognition, by Lavoisier, of the fact 
that matter is never destroyed but only takes on new forms. If a 
piece of charcoal is burned in a sealed globe large enough to con- 
tain sufficient air for the combustion, the weight of the globe 

3 



THE CHEMISTRY OF PAPER-MAKING. 



remains the same although the charcoal has disappeared. So in 
any chemical change the weight of the products of the reaction is 
always equal to the weight of the substances first concerned in it. 

This law, first formulated in regard to matter, has more recently 
been shown to be equally true of energy or force. Energy is 
never created or destroyed, but only passes from one form of 
energy into its equivalent in some other form or forms of energy. 
When coal is burned, the energy of chemical attraction is trans- 
formed into the energy of heat, which may become in succession 
the energy of steam, of a moving piston, of electricity in motion, 
to be again transformed into light and heat. These changes are 
obscure, the force which is available for our uses becomes less 
Avith each transformation, and careful experiments which take into 
account many minor changes are necessary to show that the total 
amount of force remains the same through each successive change. 

Weight and Volume. — Weight, as the term is used in chem- 
istry, means about the same as the term "mass" in physics; that 
is, it is used to denote the quantity of matter which a body con- 
tains as compared with the quantity contained in some other body 
which is taken as the unit weight. The volume of a body is the 
space which it occupies, and volumes are given in terms of some 
unit of volume. Much of what chemistry has to teach rests upon 
the accuracy of our determinations of these two functions of 
matter, and it is therefore of the first importance that the units 
employed should be as definite and convenient as possible. For 
this reason the French system of measurement, known as the 
metric system, has been universally adopted by chemists, and the 
student should familiarize himself with it at the first opportunity. 
This need require very little time, as the system is extremely 
simple. The tables will be found in the Appendix. 

Specific Gravity. — The specific gravity (or Sp. Gr.) of a sub- 
stance is the ratio between the weight of a given volume of the 
substance and the weight of the same volume of some other 
substance which is selected as the standard. Water, at its tem- 
perature of greatest density, 4° C, is the substance usually taken 
for the standard in determining the Sp. Cr. of liquids and solids, 
and we therefore mean in saying that the Sp. Gr. of sulphuric 
acid is 1.84, of lead 11.36, of alcohol 0.792, that these substances 
are respectively 1.84, 11.36, and 0.792 times as heavy as water at 
4° C, volume for volume. In some cases, for greater convenience, 



INTRODUCTION. 



water at the ordinary temperature, 15° C, is taken as the standard, 
but where this temperature has been adopted the fact is usually 
stated in giving the Sp. Gr. Various tables of Sp. Gr. will be 
found in the Appendix. 

The specific gravity or vapor density of gases and vapors is 
usually referred either to hydrogen, because it is the lightest of 
them all, or else to air, because it is most convenient. In this 
book, unless otherwise stated, the standard is hydrogen. 

The Atomic Theory. — The facts of chemistry are best ex- 
plained upon the theory, first propounded in its present form by 
Dalton, that all matter is composed of extremely minute particles 
called Molecules. A molecule is the smallest particle of a substance 
which can exist and still remain that substance. The molecules 
are themselves believed to be composed of still smaller, indivisible 
particles called Atoms, and these particles or atoms are the ulti- 
mate units with which chemistry deals and upon which chemical 
forces are exerted. The molecules of a compound substance con- 
tain two or more different kinds of atoms, which, by their associa- 
tion and arrangement, give rise to the properties which distinguish 
the substance. When, therefore, by any chemical process the 
molecule is broken up, the atoms composing it arrange themselves 
in other groups, and new substances result. The molecules of 
those simpler forms of matter, called by chemists Elements, contain 
atoms of only a single kind, but, except in one or two instances to 
be referred to in due course, the association of two or more atoms 
in the molecule is necessary to establish the qualities which char- 
acterize the elementary substance ; and if the integrity of the 
molecule is impaired, the atoms group themselves with other atoms 
to form new molecules, and again new substances are formed. 

Properties of Matter. — The different kinds of matter exhibit 
the widest possible range of qualities. The words hard, soft, light, 
heavy, crystalline, ductile, brittle, elastic, volatile, call to mind as 
many distinct qualities. The physical properties, like those named, 
depend mainly upon tlie relations of the molecules to each other 
in the substance. Chemical properties are those exhibited by a 
substance in its relations to other substances. Thus a substance 
may be inflammable or non-inflammable, acid or alkaline, soluble 
or the reverse, in various liquids. Chemical properties depend upon 
the number and kind of atoms which compose the molecule, and 
upon their arrangement within the molecule. 



THE CHEMISTRY OF PAPER-MAKING. 



States of Matter. — Matter may exist as a solid, a liquid, or a 
gas, and a very large number of substances may be made to assume 
one state or the other at will. All gases may be reduced to liquids 
and even to the solid form by the combined action of cold and 
pressure. The essential difference between the three states is 
found in the amount or range of movement which the molecules 
of a substance possess. The molecules of a substance are not 
packed together like the cells in a honeycomb, but are separated 
by spaces which are undoubtedly great in comparison with the size 
of the molecules. The whole great group of molecules which con- 
stitutes a body is held together, in a solid or liquid, by the force 
called Cohesion exerted between the molecules, and which in its 
final terms is probably similar in kind to the force which holds the 
sun and planets together. Like the stars, the molecules and atoms 
are in ceaseless motion. In a solid this motion is so limited by 
cohesion that the molecules preserve their positions relative to 
each other, and resist any force tending to displace them. In a 
liquid the molecular motion is so much greater that the cohesive 
force is nearly overcome. Still liquids have a definite surface, and 
when conditions permit assume a spherical form. In a gas the 
molecules move still more freely, and there is no cohesion between 
the molecules. The molecules of a gas tend to diffuse equally in 
all directions. 

Differences in what we call the temperature of a bod}- are differ- 
ences in the momentum of the moving molecules. These differ- 
ences are measured in an arbitrary way by the thermometer. When 
we heat a body we expend force upon it to increase the momentum 
of its molecules, and conversely, when a body is cooled, the momen- 
tum of its molecules is gradually distributed among those of the 
cooling agent. 

Change of State. — Bearing the facts of the last two para- 
graphs in mind, it becomes evident how, through the action of 
heat, a solid body may be converted into a liquid and finally into 
a gas ; and also how the volume of a substance increases as its 
temperature rises. 

In order to bring about this change from the solid to the liquid 
state, or from the liquid to the gaseous state, it is necessary to 
move the molecules apart sufficiently to limit in the first case, and 
entirely overcome in the second, the force of cohesion. This is 
accomplished by the power supplied by heat. In other words, 



INTRODUCTION. 



heat is absorbed during both these changes. Ice at zero centi- 
grade may be heated for some time, and the result is water at 
zero. Water at 100° C. requires much heat to convert it into 
steam at 100° C. The heat thus absorbed is given out again 
when the molecules resume their former positions, and is therefore 
called Latent Heat. Different substances have different latent 
heats. Similarly, equal weights of different substances require 
different quantities of heat to produce the same rise of tem- 
perature. Water requires more than almost any other substance, 
and the quantity of heat needed to raise one kilogramme (2.2 lbs.) 
from 0° to 1° C. is called one unit of heat. It is the moving force 
developed by 423 kilogrammes falling one metre (3 ft. 3f in.). 
The Specific Heat of a substance is the proportion between the 
quantity of heat needed to raise the temperature of a given weight 
of the substance through one degree and the quantity of heat 
needed to raise the temperature of an equal weight of water 
through one degree. 

Gas Pressure. — Since the molecules of a gas are free to move 
in straight paths, it follows that the molecules are constantly 
bombarding the walls of any containing vessel. These blows, by 
their aggregate effect, produce the phenomena of gas pressure. If 
the rapidity of motion is increased by heat, the impacts are more 
violent and the pressure rises. If the volume of the vessel is 
decreased, more molecules strike the walls and the pressure simi- 
larly rises. The power of the steam-engine is derived from the 
blows delivered against the piston by the infinite number of mole- 
cules of water as their motion is arrested by its face. 

Compounds and Elements. — By the processes of chemical 
analysis nearly every known substance may be made to yield two 
or more simpler bodies. Substances which may be thus decom- 
posed are termed Compounds. About seventy substances are 
known to chemists which have so far resisted all attempts to 
resolve them into anything simpler. Such simple substances 
are called Elements. The elements exhibit every diversity of 
character. Some, like oxygen and chlorine, are gases ; others, 
like bromine and mercury, are liquids at ordinary temperatures. 
The great majority are solids. Only about one-half of them are 
of common occurrence. 

The Law of Ampere. — Various experimentalists have shown 
that all gases expand and contract equally under the same 



THE CHEMISTRY OF PAPER-MAKING. 



variations of temperature and pressure. From this fact it follows, 
as a mathematical consequence, that equal volumes of all gases, 
under the same conditions of temperature and pressure, contain the 
same number of molecules. This deduction, which is of great 
importance in the theory of chemistry, is called the Law of 
Ampere. 

Atomic Weights. — In order that chemical calculations may be 
accurately performed, it is of the first importance that the relative 
weights of the atoms composing the different elementary sub- 
stances should be accurately determined, since combination takes 
place between atoms. Hydrogen is the lightest of all known 
substances, and the weight of the hydrogen atom is therefore 
taken as the unit in which the weights of all the other atoms are 
expressed. The atomic weight of oxygen is given as 16 — this 
means that an atom of oxygen is 16 times as heavy as an atom of 
hydrogen. The molecular weight of a substance is the sum of the 
weights of the atoms which compose the molecule, and is of course 
dependent upon the number and kind of atoms which the molecule 
contains. A table giving the atomic weights of the different 
elements will be found in the Appendix. 

Although these weights are only relative weights, they are none 
the less real, and many of them have been determined with the 
most refined accuracy. Their value rests upon data of several 
kinds, and which are in large measure independent of each other. 
First, the law of Ampere gives us a means of rinding the molecular 
weight of any substance which can be brought into the state of 
gas. We know by the results of chemical analysis that the 
molecule of hydrogen contains two atoms, and that its molecular 
weight is therefore 2. Since equal volumes of different gases 
contain the same number of molecules, it follows that the molecular 
weight of any substance is equal to twice its specific gravity in 
the state of gas. For example, oxygen is 16 times as heavy as 
hydrogen, volume for volume ; that is, the Sp. Gr. of oxygen is 
16, and the oxygen molecule must weigh 16 times as much as 
the hydrogen molecule : 16 X 2 — 32, the molecular weight of 
oxygen. 

Second, by analysis of the different compounds of an element, 
and comparison of the results, we are able to find those compounds 
in which the element enters into combination in smallest propor- 
tion, and such compounds are therefore believed to contain only 



INTRODUCTION. 9 



one atom of this element in a molecule of the compound. Thus 
twice the Sp. Gr. of hydrochloric acid gas gives 36.5 as the molec- 
ular weight, and 36.5 parts of the acid by weight yield one part 
of hydrogen. None of the immense number of hydrogen com- 
pounds yield on analysis less than one part by weight of this ele- 
ment, where amounts which are proportional to the molecular 
weight of the compounds are taken for analysis. Some give two, 
three, four, or more times this quantity, and are therefore believed 
to contain two, three, four, or more atoms of hydrogen in the mole- 
cule, as the case may be. 

Third, we find, for example, that one volume of hydrogen com- 
bines with one volume of chlorine to form two volumes of hydro- 
chloric acid gas ; therefore one molecule of hydrogen combines with 
one molecule of chlorine to form two molecules of hydrochloric 
acid. This acid contains the smallest proportion of chlorine which 
enters into combination, as well as the smallest proportion of 
hydrogen ; that is, one molecule of the acid contains an atom of 
hydrogen and an atom of chlorine. It follows, then, that if one 
molecule of hydrogen forms, with one molecule of chlorine, two 
molecules of the acid, the molecule of each element must contain 
two atoms. Twice the Sp. Gr. of chlorine gas is 71, which is the 
weight of this molecule containing two atoms. The weight of the 
single atom is therefore 35.5, and no compound of chlorine is known 
which does not give this quantity or some multiple of it, when 
an amount proportional to the molecular weight of the compound 
is analyzed. 

Fourth, the relations of the atoms to heat furnish another means 
by which the atomic weights may be checked, since it is true that 
the quantity of heat required to raise the temperature of an atom 
one degree is the same for all atoms. We believe that 16 grammes 
of oxygen contain as many atoms as one gramme of hydrogen, since 
an atom of oxygen is believed to be 16 times as heavy as one of 
hydrogen. If this belief is correct, it should require the same 
amount of heat to raise the temperature of a gramme of hydrogen 
one degree as to raise the temperature of 16 grammes of oxygen 
one degree, and experiment proves that such is the case. 

The Law of Definite Proportions. — Chemical combination 
always takes place in definite proportions, and such proportions 
appear whether we regard the weights of the substances concerned 
or their volumes in the state of gas. In this fact is found one of 



10 THE CHEMISTRY OF PAPER-MAKING. 

the strongest proofs of the correctness of the atomic theory, for 
the fact can only be explained upon the assumptions that combina- 
tion takes place between atoms and that the atoms have definite 
weights. Two volumes of hydrogen combine with one volume of 
oxygen to form two volumes of steam, and the law of Ampere 
points out the simple numerical relation existing between the 
number of molecules of each substance and consequently between 
the number of atoms concerned. If by accident or design any 
excess of either gas is present, it remains unchanged. Since the 
atoms have definite weights, combination between them must 
always take place in a definite proportion by weight. A molecule 
of water alwaj^s contains two atoms of hydrogen, and one atom of 
oxygen and 18 parts by weight of water must therefore always 
yield two parts by weight of hydrogen and 16 parts by weight 
of oxygen. 

Mixtures and Chemical Compounds. — The facts of the last 
paragraph enable us to determine whether a substance under exam- 
ination is a mixture or a chemical compound. The proportions of 
the different substances which enter into a chemical compound are 
always fixed and definite, and the compound itself is different from 
either or any of its components. Heat, moreover, is usually devel- 
oped when substances combine chemically. Mixtures may take 
place in all proportions ; no heat is developed unless there is some 
accompanying chemical action, and the properties of the mixture 
bear some obvious relation to those of its ingredients. Simple me- 
chanical means are usually sufficient to separate a mixture. Gun- 
powder, for example, is a very perfect mixture of sulphur, nitre, and 
charcoal. The proportion of each varies with the country and pur- 
pose for which the powder is made. The separate particles of each 
component may be distinguished under the microscope. Mere wash- 
ing with water will remove the nitre, and the sulphur may be dis- 
solved in bisulphide of carbon, leaving the charcoal by itself. When 
the powder is exploded, chemical compounds are formed which 
differ completely in their character from any of the ingredients of 
powder, and if more charcoal, for example, is present than was 
needed to form these compounds, the excess will remain as char- 
coal until it reaches the air. 

Chemical Symbols. — In order to represent the constitution of 
substances as clearly and concisely as possible, chemists have 
adopted a system of notation in which the initial letter of the 



INTRODUC TION. 1 1 



Latin name of the different elementary substances is made to 
represent one atom of the element. Thus one atom of hydrogen 
is represented by H ; one atom of sulphur, by S ; one atom of oxygen, 
by O. Where several elements would otherwise have the same 
symbol, an additional letter is added to avoid confusion. C stands 
for one atom of carbon ; CI, for an atom of chlorine ; Na, for an 
atom of sodium (natrium). A table of the elements, giving their 
symbols and atomic weights, will be found in the Appendix. 

When it is wished to represent several atoms of the same kind, 
the appropriate figure is placed to the right of and below the 
symbol ; thus, H 2 represents two atoms or a molecule of hydrogen ; 
S 6 , six atoms of sulphur. The composition of a compound sub- 
stance is shown by grouping together the symbols of its component 
atoms with the figures showing the number of each kind of atom : 
thus, HC1 stands for one molecule of hydrochloric acid, and 
shows that the molecule is composed of an atom of hydrogen 
and an atom of chlorine ; H 2 stands for water or a molecule 
of water, which contains two atoms of hydrogen and one of 
oxygen ; H 2 S0 4 stands for a molecule of sulphuric acid, which is 
composed of two atoms of hydrogen, one of sulphur, and four of 
oxygen. 

In order to represent several molecules of the same substance 
it is customary to use a large figure on the line and to the left of 
the symbols which represent a single molecule ; thus, 2 Na 2 C0 3 
stands for two molecules of soda-ash. Parentheses and a small 
number to the right are sometimes used for the same purpose; 
thus, (Na 2 C0 3 ) 2 : but this form is usually limited to cases where 
the symbols or formulas of several different molecules are grouped 
together, and the small number outside the parenthesis indi- 
cates that everything inside the parenthesis is to be multiplied 
accordingly. 

Since the atoms have definite weights, the symbol which 
represents the number and kinds of atoms in a molecule also 
represents the proportion by weight in which each element occurs 
in the molecule ; and since the mass of a compound is made up 
of similar molecules the symbol also stands for the kinds and 
proportions of the elementary substances composing the compound 
substance. For example, in the case of the symbol Na 2 C0 3 just 
given for soda-ash, a reference to the table of atomic weights 
shows that the atomic weight of sodium, Na, is 23 ; of carbon, 12 ; 



12 THE CHEMISTRY OF PAPER-MAKING. 

of oxygen, 16. The proportion by weight in which the different 
elements occur in the molecule is then : — 

Sodium, N"a 23 x 2 = 46 

Carbon, C 12 x 1 = 12 

Oxygen, ........ 16 x 3 = 48 

106 

The molecular weight of soda-ash (sodium carbonate) is therefore 
106, and in the molecule there are 46 parts by weight of the metal 
sodium, 12 parts of carbon, and 48 parts of oxygen. Any quantity 
of sodium carbonate. is merely an aggregation of similar molecules, 
and therefore the proportions by weight which are true of the 
molecule are also true of any quantity of the compound. 

Chemical symbols, furthermore, indicate the proportions in 
which combination by volume occurs when the substances are in 
the state of gas ; for, bearing the law of Ampere in mind, each 
molecule represented by the symbols represents a unit volume of 
the gas. 

2 mols. of hydrogen. 1 mol. of oxygen. 2 rools. of steam. 

2H 2 + 3 = 2H,0 

or two volumes of hydrogen combine with one volume of oxygen 
to form two volumes of steam. 

The Law of Multiple Proportions. — Among the compounds 
of chlorine there are four which are known to have the composi- 
tion represented by the formulas : — 

HCIO, HC10 2 , HCIO., HC10 4 . 

These are the only known compounds of chlorine which contain 
these three elements and no other. Nearly all the elements 
combine with each other in more than one proportion, but there 
is always in such cases a simple numerical ratio between the pro- 
portions in which the elements occur in the different compounds. 
If we select the compound containing the least of one of the 
elements which combines thus in several different proportions, the 
proportions in the other cases are simple multiples of the pro- 
portion present in the one selected. In the case given above 
there is present in each compound 35.5 parts by weight of 
chlorine, while the amount of oxygen is, as the compounds are 
successively considered, 16, 32, 48, 64 parts by weight, and these 
numbers bear the same ratio as 1, 2, 3, 4. This law of multiple 



INTRODUCTION. 13 



proportions, though first shown by the results of chemical analysis, 
is an evident consequence of the fact that combination always 
takes place between atoms. 

Chemical Equivalents. — The same quantity of any acid which 
is needed to neutralize 40 parts by weight of caustic soda will 
neutralize 28 parts of lime or 20 parts of magnesia, and the same 
quantity of any of these alkalis which will neutralize 36.5 parts 
by weight of gaseous hydrochloric acid will neutralize 49 parts of 
sulphuric acid or 63 parts of nitric acid. Quantities of different 
substances which are found by experiment to stand in this relation 
to each other are termed chemical equivalents. 

Quantivalence. — A reference to the symbols given below, which 
of course represent the composition of the compounds as determined 
by analysis, reveals an important fact : — 

HC1 Hydrochloric acid 

H 2 Water 

H 3 N^ Ammonia 

H 4 C Marsh gas 

We find, that whereas an atom of chlorine, CI, combines with or 
fixes one atom of hydrogen, H, an atom of oxygen, O, fixes two, 
an atom of nitrogen, N, fixes three, and an atom of carbon, C, fixes 
four of hydrogen. This attractive or atom-fixing power, which 
varies with the atoms of different elements, is termed the quan- 
tivalence of the atom. An atom which either combines with or 
replaces a single atom of hydrogen is called a univalent atom; 
one which combines with or replaces two atoms of hydrogen, or 
another univalent substance, is termed bivalent ; if the fixing 
power extends to three or four atoms of a univalent substance, the 
atom is trivalent or quadrivalent, as the case may be. 

The quantivalence of the atoms is believed to be due to a sort of 
polarity, the attractive power of each pole being sufficient to hold 
in the molecule a single univalent atom. These poles or bonds 
are often represented by short lines radiating from the symbol of 
the atom, and the symbols given above are then written thus : — 

H H 

I I 

H-Cl H-O-H H-N H-C-H 

I I ■ 

H H 



14 THE CHEMISTRY OF PAPER-MAKING. 

Just as the two poles of a magnet may neutralize or satisfy each 
other, so, under certain circumstances, two of these atomic poles 
may satisfy each other, and the same atom may in its different 
combinations exhibit different atom-fixing powers. Thus we have : 

Ammonia. Chloride of ammonia. 

H H 

I H | 

H-N ^N-Cl 

I H X | 

H H 

and the two chlorides of phosphorus : — 

CI CI 

I CI I 

ci-p >_C1 

i cr i 

ci ci 

Manganese and fluorine form four compounds, and the proportions 
and quantivalence of the atoms in each case are shown in the 
symbols given below : — 

F 
I 
F-Mn-F F-Mn-F 

I 
F 



F F 


F F 


1 1 


\ / 


F-Mn-Mn-F 


F-Mn-F 


1 1 


/ \ 


F F 


F F 



Since whenever the quantivalence varies, tAvo poles must either 
neutralize or free each other, the atom-fixing power is either 
always even or always odd, and a comparison of all the symbols 
given under this head brings out this fact. Symbols, like those 
immediately above, are called Grraphic Symbols, and they are much 
used to represent, as clearly as may be, the arrangement of the 
atoms in the molecule. 

Nomenclature. — The number of substances known to chem- 
istry is so immense that their study is greatly facilitated, by a 
system of naming them, which not only arranges them in groups, 
but indicates their composition. The names of all the more 



IN TB OD UCTION. 1 5 

recently discovered metals end in -ium or -um, as sodium, potas- 
sium, platinum. The names of various groups of non-metallic 
elements have distinctive endings, as carbon, boron, silicon ; chlo- 
rine, bromine, iodine, fluorine. In many cases, however, both 
among metals and non-metals, old names persist, as iron, silver, 
sulphur, phosphorus. Compounds of oxygen and another ele- 
ment are called oxides, similar compounds of sulphur are called 
sulphides, and most of the non-metallic elements form with 
another element compounds whose names end in -ide. Thus 
chlorine, bromine, iodine, fluorine form chlorides, bromides, io- 
dides, fluorides respectively. The proportion of the non-metallic 
element present is indicated by the prefixes di- (or 6i-), tri-, tetra-, 
penta-, as appears in the examples below : — 

Manganese dioxide Mn0 2 

Phosphorous trioxide P2O3 

Tin tetrachloride SnCl 4 

Phosphorous pentoxide P2O5 

The different atom-fixing power of an element is often indicated 
by the endings -ous and -ic of its Latin name. Thus iron (ferrurn) 
forms ferrous chloride, FeCl 2 , and ferric chloride, Fe 2 Cl 6 . Tin 
(stannum) forms stannous chloride, SnCl 2 , and stannic chloride, 
S11CI4 ; and in such names -ous indicates the lower degree of atom- 
fixing power or quantivalence, and -ic the higher. 

Compounds of the metals with oxygen, or oxides of the metals, 
are called Bases, and the same term is applied to compounds of the 
metals with oxygen and hydrogen or hydrates of the metals. The 
bases possess, in a more or less marked degree, those properties 
which are termed alkaline. They unite with acids to form Salts. 

Compounds of the non-metallic elements which contain hydro- 
gen which may be replaced by a metal are termed Acids. 
Hydrochloric acid, HC1, for example, contains an atom of hydro- 
gen, which may be replaced by a metal, like sodium, to form, in 
this case, sodium chloride, NaCl, common salt. Sulphuric acid 
contains two atoms of hydrogen, which may be thus replaced by 
two univalent atoms like sodium to form sodium sulphate, Na 2 S0 4 , 
or by one bivalent atom like zinc to form zinc sulphate, ZnS0 4 . 
An acid is termed monobasic, dibasic, and so on, according as it 
contains one, two, or more hydrogen atoms which may be thus 
replaced. Whether the hydrogen atoms can be replaced by a 



16 THE CHEMISTRY OF PAPER-MAKING. 

metal depends on their position in the molecule. Acetic acid, 
C 2 H 4 2 , is a monobasic acid ; while oxalic acid, C 2 H 2 4 , is a bibasic 
acid. This difference is shown in the graphic symbols of these 
compounds : — 

Acetic acid. Oxalic acid. 

H O 

II I II II 

H-O-C-C-H H-O-C-C-O-H 

I 
H 

It will be noticed that three of the hydrogen atoms in acetic acid 
are shown in a different relation to the carbon atoms than that 
occupied by the other one, and we find by experiment that these 
three atoms can be replaced by a non-metallic element like 
chlorine, but not by a metal. The graphic symbol is deduced 
from the results of such experiments. In the molecule of oxalic 
acid, however, both hydrogen atoms occupy the same position 
relative to the molecule that the atom of hydrogen which can 
be replaced by a metal occupies in acetic acid. Both of these 
atoms can be replaced by a metal, but not by a non-metal like 
chlorine. 

This illustrates again the general truth that the properties of 
a substance depend quite as much upon the arrangement of the 
atoms in the molecule as upon the number and kind of the atoms 
themselves. 

Compounds which contain no hydrogen, but which unite with 
the elements of water to form bases or acids, are called Anhydrides, 
the word meaning, without water. Sulphuric anhydride, S0 3 , for 
instance, is a snow-like solid which combines with water, H 2 0, to 
form sulphuric acid, H £ S0 4 . 

When the same elements combine in different proportions and 
form more than one acid, the suffix -ous is used to indicate the 
lower stage of oxidation, and -ic to indicate the higher. We have 
chlorous acid, HC10 2 , which forms chlorz'tes, and chloric acid, 
HC10 3 , which forms chlorates. In case there are other acids the 
prefixes hypo- and per- are added, the first to indicate the lowest 
and the last the highest stage of oxidation. Thus we have hypo- 
chlorous acid, HCIO, which forms hypochlorites, and perchloric 
acid, HC10 4 , which forms perchlorates. 



INTRODUCTION. 17 



Reactions and Equations. — The changes which occur when 
two or more substances react upon each other chemically, or when 
one is decomposed by heat or otherwise, may be represented by 
chemical symbols arranged in the form of equations. Caustic 
soda and hydrochloric acid combine to form sodium chloride and 
water, and the reaction may be written — 

Caustic soda + Hydrochloric acid = Sodium chloride + Water. 

NaOH + HC1 = XaCl + H 2 0. 

Upon examining this equation, and any properly written one, we 
find that the sum of the atomic weights of the factors on one side 
is the same as the sum of the atomic weights of the products on 
the other. The same number of atoms of" each kind also must 
appear on each side of the equation. 

It must be borne in mind that these equations are not arbitrary 
formulas which the atoms are expected to follow, but that they are 
written to express what, so far as we know, actually does occur; 
and such an equation, to be useful, must take into account the 
known relations and chemical properties of all the substances con- 
cerned and their components. 

When there are several possible reactions, that one, if any, in 
which a gas is evolved, or an insoluble substance formed, is the 
one most likely to occur. Solution in a liquid, by overcoming the 
cohesion of the molecules and leaving them more free to move 
within range of each other's influence, promotes chemical change 
and often determines the course of the reaction. A rise of tem- 
perature has the same effect in promoting chemical activity, because 
it means that the moving power of the molecules is increased. At 
the instant in which an atom is liberated from one combination, 
and before it has entered into another, the atom is said to be in the 
nascent state ; and since all its affinities are during that instant 
unsatisfied, its chemical properties are thus intensified. For ex- 
ample, in the reaction of sulphuric acid upon zinc, — 

Zn + H,80 4 = ZnSO, + H 2 , 

two atoms of hydrogen are liberated which ordinarily combine at 
once to form the molecule of hydrogen, H-H ; but if another sub- 
stance is present upon which the just liberated atoms can react be- 
fore mutually satisfying each other, they are likely to so. react much 
more powerfully than after their union in the molecule H-H. 



18 THE CHEMISTRY OF PAPER-MAKING. 

When an electric current is passed through water the following 
decomposition occurs : — 

2H 2 = 2H 2 + 2 . 

When limestone, calcium carbonate, CaC0 3 , is heated, it splits up 
into caustic lime, CaO, and free carbonic acid gas, thus : — 

CaC0 3 = CaO-fC0 2 . 

Such reactions, in which a substance is separated into two or more 
simpler ones, is called an Analytical Reaction; and analytical 
processes are those which seek to separate a substance into its 
constituents, or to otherwise determine what its constituents are. 
Synthetical processes are those by means of which a substance is 
transformed into another more complex one by the addition of 
new atoms in the molecule. The following are examples of 
synthetical reactions : — 

S 8 + 2 0j = 2SO B , 
H 2 + C1 2 =2HC1. 

There is another very common form of reaction in which certain 
of the atoms merely exchange places in different molecules. For 
example, in the manufacture of Pearl Hardening — 

/-, , • ., ., o i- i u » Sodium chloride , Calcium sulphate, 

Calcium chloride + Sodium sulphate = ? mols _ + pear , harde P niug .* 

CaCL + Na 2 S0 4 = 2 NaCl + CaS0 4 . 

Stochiometry. — When the chemical symbols and reactions are 
understood, ordinary chemical calculations require only the applica- 
tion of the simplest rules of arithmetic, and can usually be solved 
by the rule of proportion. The following rules will be found useful. 
The relations upon which they depend have been already discussed 
in the preceding sections. 

1. The molecular weight is equal to the sum of the weights of the 
atoms composing the molecule. 

2. The percentage of any constituent in the molecule is found by 
multiplying the weight of the constituent by 100 and dividing by the 
weight of the molecule ; or, 

Wt. of constituent : Wt. of Mol. = a; : 100. 



._> 



INTRODUCTION. 19 



3. The proportion of any ingredient in a mass of a compound is 
the same as the proportion of the ingredient in a molecule of the 
compound. 

4. In any chemical reaction the toted weight of the products is 
equal to the sum of the weights of the substances first concerned. 

5. If any chemical operation is expressed in the form of an 
equation, and the molecular weights of all the substances concerned 
are then written below their respective formulas, the following 
rule will be found sufficient for most problems : — 

As the molecidar weight of the substance given is to the molecular 
weight of the substance required, so is the weight (in pounds, 
grammes, etc.) of the substance given to the weight of the substance 
required. 

In case the equation shows that more than one molecule of a 
given substance is concerned in it, the molecular weight of that 
substance should be multiplied accordingly, for the purposes of the 
above rule. 

EXAMPLES. 

1. What is the molecular weight of common salt ? 
Symbol of common salt is NaCl. 

Ans. Na = 23 ; CI = 35.5 ; XaCl = 58.5. 

2. What is the molecular weight of caustic soda, NaOH ? Ans. 40. 

3. What is the molecular weight of sulphuric acid, H 2 S0 4 ? Ans. 98. 

4. What is the molecular weight of carbonate of soda, soda-ash, 
Na 2 C0 3 ? Ans. 106. 

5. What is the molecular weight of bisulphite of lime, H 2 CaS 2 6 ? 

Ans. 202. 

6. How much chlorine is contained in 1170 lbs. of common salt ? 
Since ISTaCl = 58.5, every 58.5 lbs. of salt contain 35.5 lbs. of chlorine. 

Ans. 710 lbs. 

7. What per cent, of sulphur is there in sulphurous acid gas, S0 2 ? 

S = 32, O = 16, S0 2 = 32 + 16 + 16 = 64. 
Wt. of S 32 : wt. of SOj 64 = x : 100. 
32 x 100 



64 Ans. 50%. 



20 THE CHEMISTRY OF PAPER-MAKING. 

8. What is the per cent, of alumina, A1 2 3 , in pure crystallized potash 
alum, K 2 A1 2 S 4 16 , 24 H 2 ? 

Al 2 27.4 x 2 = 54.8 K 2 39.1 x 2 = 78.2 

3 16. x 3 = J8^ Ah 27.4 x 2 = 54.8 

Mol. wt., Al 2 Oo = 102.8 S 4 32. x 4 = 128.0 

16 16. x 16 = 256.0 

517.0 

24 H 2 (2 + 16) x 24 = 432.0 

Mol. wt. potash alum = 949.0 

102.8 x 100 _ „, Ain 

9. How much water, H 2 0, is there in 2000 lbs. of crystallized potash 
alum ? 

Ex. 8 shows that 24 H 2 = 432, while the molecular weight of 
potash alum is 949. 

432 : 949 = x : 2000. Ans. 910.4 lbs. 

10. How many pounds of sulphurous acid gas will be formed by the 
combustion of 420 lbs. of sulphur, supposing the loss of sulphur as ash, 
and by sublimation, to amount to 10 per cent. ? 

420 lbs. less 10% =378 lbs. available. 

S 32 : S0 2 64 = 378 : x. Ans. 756 lbs. 

11. The formula of Pearl Hardening, or crystallized sulphate of 
lime, as it occurs in paper, is CaS0 4 , 2 H 2 0. In burning the paper to 
determine the amount of filler, this combined water (2 H 2 0), which 
really adds so much to the weight of the paper, is driven off, so that 
the formula of the ash as weighed is CaS0 4 . What correction should 
be applied to the per cent, of ash found in order that it may show the 
amount of Pearl Hardening really in the paper ? 

Mol. wt., CaS0 4 , 2 H 2 = 136 + 36 = 172 ; 
CaS0 4 = 136. 

136 parts of ash, CaS0 4 = 172 parts of filler, CaS0 4 , 2 H 2 0. 

172 

—— = 1.26; therefore every 1% of ash = 1.26% of filler, 

J-OO 

and per cent, of ash should be multiplied by 1.26 in order to obtain 
per cent, of filler in paper. 

12. How many pounds of pure sulphuric acid, H 2 S0 4 , are needed to 
dissolve 100 lbs. of zinc, the reaction being — 

Zn + H 2 S0 4 = ZnS0 4 + H 2 ? 
65 98 

The proportion, then, is 65 : 98 --= 100 : x. Ans. 151 lbs. 



IN TB OD UCTION. 21 



13. If in burning 420 lbs. of sulphur to make sulphite liquor 10 per 
cent, of the sulphur is converted into sulphuric acid, how much lime 
will this neutralize in forming the useless sulphate of lime ? The 
reaction may be considered for the purposes of the problem — 

CaO + H 2 S0 4 = CaS0 4 + H 2 0. 
5(i 98 Ans. 73.5 lbs. 

14. The formula of soda-ash is Na 2 C0 3 ; of soda crystals, Na 2 C0 3 , 
10 H 2 0. One molecule of each combines with the same amount of 
rosin. If 40 lbs. of Na 2 C0 3 are required to make a certain quantity 
of size, how much iSJ"a 2 C0 3 , 10 H 2 will be needed to make the same 
amount ? Ans. 108 lbs. 

15. Lime, CaO, in contact with water slakes to form calcium 
hydrate, CaH 2 2 . How much lime would be required to causticize 
2000 lbs. of soda-ash, ]STa 2 C0 3 , according to the reaction — 

Na 2 C0 3 + CaH 2 2 = CaC0 3 + 2 NaOH ? Ans. 1056.6 lbs. 

16. 560 kilos of lime are required to make a certain quantity of 
sulphite liquor. How many kilos of limestone, carbonate of lime, 
CaC0 3 , will be required to make the same amount of liquor? One 
molecule of lime will make as much liquor as one molecule of 
limestone. Ans. 1000 kilos. 



Part T. 
GENERAL CHEMISTRY. 



Paet I. 



GENERAL CHEMISTRY. 



THE NON-METALLIC ELEMENTS. 



OXYGEN. 

Symbol, O. — Atomic weight, 16. — Molecule, 0-2. — Molecular weight, 32. 

Oxygen is by far the most important of all the elementary 
chemical substances, as well as the most abundant, both in the 
free state and in combination with other substances. 

Free oxygen is a colorless, tasteless, and odorless gas. It forms 
in the free state about one-fifth by measure and about one-quarter 
by weight of dry air. In combination with hydrogen as water it 
constitutes eight-ninths of the weight of the latter substance, and 
in combination with various substances it has been estimated to 
constitute about one-eighth of the total weight of the entire globe. 
In the free or gaseous state oxygen is necessary to respiration, the 
germination of seeds, the growth of plants, the decay of vegetable 
substances, and the commencement of putrefaction in animal 
matters. It is also necessary for the support of combustion, 
though it is itself uninflammable. Oxygen is the most magnetic of 
all gases ; the daily variations of the magnetic needle are probably 
caused by the effect of heat in changing the magnetic properties 
of the gas. Oxygen is only slightly soluble in water, 100 volumes 
of water dissolving 2.99 volumes at 15° C. and 4.11 volumes at 0° C. 
under the ordinary pressure of the atmosphere. 

The weight of oxygen, as compared with an equal volume of 
dry hydrogen, or its specific gravity, is 15.96. Pure oxygen may 
be prepared by heating many of its compounds — as manganese 
dioxide, Mn0 2 , or potassium chlorate, KC10 3 — in a closed vessel 
to a temperature sufficiently high to decompose the compound, 

25 



26 GENERAL CHEMISTRY. 

when oxygen will be given off and may be collected by suitable 
means. It may also be obtained through the decomposition of 
water by means of the electric current. When a clear solution of 
bleaching-powder, to which have been added a few drops of a 
solution of any cobalt salt, is heated to about 80° C, oxygen is 
easily and regularly evolved in considerable quantity. If the 
solution is milky, or if a paste made with bleaching-powder and 
water is used with the cobalt solution, it is necessary to add a 
little paraffin oil to prevent frothing. Oxygen was first prepared 
by Priestley in 1774 by heating mercuric oxide, HgO. 

The process of union, or of combination of oxygen directly with 
another substance, is called combustion or oxidation ; and the 
products of such combustion are called Oxides. The weight of the 
products of combustion is always equal to that of the substance 
burned plus the weight of the oxygen consumed (combined or 
fixed) in the process. Combustion may be either dry, as in the 
burning of coal in a grate, or moist, as in the combustion (destruc- 
tion) of coloring-matters in the process of bleaching. In the 
latter case the oxygen of the bleaching-powder, Ca(C10) 2 , com- 
bines with the coloring-matters to form eventually dioxide of 
carbon or carbonic acid, C0 2 , and water. Combustion, whether 
moist or dry, is always attended with sensible increase of tem- 
perature, varying directly with the rapidity of the chemical com- 
bination. Conversely, sensible increase of temperature always 
increases the rapidity of combustion. This explains the phenome- 
non of spontaneous combustion. This only takes place with easily 
combustible substances and those which by their physical con- 
ditions expose a large surface to the action of the oxygen of the 
air, as, for instance, oily waste or fur. When a mass of waste 
saturated with an easily combustible oil is thrown carelessly in a 
warm place where it is exposed to the air, combination of the 
oxygen with the oil at once begins and heat is developed. This 
in turn increases the rapidity of the combination, which generates 
more heat, until after a time the mass becomes hot enough to 
smoulder and then burst into flame. If, however, the supply of 
oxygen is limited, as is the case when the waste is enclosed in a 
tight case, the combustion will be limited to the consumption of 
the oxygen within the case, and the heat can never rise to the 
inflaming-point. Spontaneous combustion can never occur in such 
materials loosely exposed or spread out to the air, since in that 



HYDROGEN. 27 



case the currents of air and large radiating surface exposed keep 
the temperature always below the inflaming-point by carrying off 
the heat as fast as it is generated. Mineral oils have no tendency 
to spontaneous combustion, and when present in a mixed oil 
greatly lessen the danger from this source. When the proportion 
of mineral oil reaches 30 per cent, there is no danger. 

When sparks from an electric machine are passed through 
ordinary oxygen, three volumes of the gas are condensed into two, 
the gas at the same time acquires a peculiar odor, and has its 
characteristic chemical properties intensified in a marked degree. 
The same change may be brought about in several other ways. 
This condensed oxygen is called allotropic oxygen or ozone. 
When heated to 290° C. it is instantly converted into ordinary 
oxygen. Ozone is produced in nature by the action of the air on 
gums and resins, but is instantly decomposed by contact with 
putrescent matters. The gradual deterioration of rosin-sized 
paper is believed to be due in part to the effect of ozone, formed 
by the action of the air upon the rosin size. Ozone may often be 
detected in minute quantities in the air of the country, and espe- 
cially in the vicinity of pine forests, but is almost never present in 
the air of thickly settled towns. 

It is a very energetic bleaching agent, and many attempts have 
been made to produce it on a manufacturing scale for that pur- 
pose, but none have met with commercial success. 

HYDROGEN. 

Symbol, H. — Atomic weight, 1. — Molecule, H 2 . — Molecular weight, 2. 

Hydrogen is a colorless, tasteless, and odorless gas. As usually 
prepared, however, it always contains slight traces of other sub- 
stances which impart to it various odors more or less disagreeable, 
and characteristic of the different impurities. It is the lightest 
of all known substances, and on that account the weight of the 
hydrogen atom is taken as the unit or standard of atomic weights. 
A given volume of the gas weighs only 0.0691 as much as an 
equal volume of air. Hydrogen is inflammable when heated in air, 
combining with the oxygen to produce hydrogen oxide, H,0, 
water. The hydrogen flame produces very little light, being of a 
faint bluish color, but a very intense heat. 

By leading hydrogen and oxygen gases, under pressure, through 



28 GENERAL CHEMISTRY. 

separate tubes, and allowing them to mix in the proper proportions 
at the point of ignition, a heat may be produced second only to 
that of the electric arc. This flame, known as the oxyhydrogen 
flame, and the instrument for its production as the oxyhydrogen 
blowpipe, is made use of in the production of the calcium light, 
which was the most powerful light known previous to the inven- 
tion of the electric light. In the production of the calcium light 
the flame from the oxyhydrogen blowpipe is directed upon a cyl- 
inder of compressed lime, raising the latter to such an intense heat 
that it emits a dazzling white light. 

The oxyhydrogen blowpipe, or more often one in which air is 
used in place of oxygen, is also invaluable to the plumber, who 
employs it in fusing together two pieces of lead into a single piece, 
the operation being technically called lead-burning. 

Hydrogen when mixed with air or oxygen in any quantity, as in 
a flask or bottle, forms a mixture which will explode with terrific 
force when fire is brought into contact with it. For this reason 
one should always be sure, when using the gas, that it is coming 
from the generator pure, or unmixed with air, before applying a 
light to the stream of gas. 

Hydrogen is but slightly soluble in water. Iron, at a red heat, 
is penetrated by hydrogen. The gas is not poisonous, and may be 
breathed, when pure, for a short time, without ill effects. It has a 
curious action, however, on the organs of speech, raising the pitch 
of the voice very noticeably after a few inspirations. 

Hydrogen occurs chiefly in combination with oxygen as water ; 
it also occurs in the larger number of organic bodies with oxygen 
and carbon, and sometimes nitrogen ; and with carbon alone in the 
mineral oils. It forms the chief element, as shown by the spectro- 
scope, in the atmosphere of many of the stars. 

Hydrogen may be obtained by the electrolysis of water, or by 
passing steam over red-hot iron, the oxygen of the water unit- 
ing with the iron to make oxide of iron, and leaving the hydrogen 
free. 

Certain metals, notably sodium and potassium, have the power 
of decomposing water at ordinary temperatures, with the formation 
of an oxide of the metal and free hydrogen. The easiest as well 
as least expensive method of preparing hydrogen in quantity is by 
the action of a metal, preferably zinc, on muriatic or sulphuric acid 
diluted with water. In this case the metal takes the place of 



NITROGEN. 29 



hydrogen in the acid, forming chloride or sulphate of the metal, 
and free H 2 , as shown in the equation — 

H 2 S0 4 + Zn = ZnS0 4 + H 2 . 

This latter is the method used by plumbers in preparing hydro- 
gen for use in lead-burning. 

The most common, as well as the most important, compound of 
hydrogen is water, hydrogen oxide, H 2 0. 

Water is a clear transparent liquid, colorless in small quantities, 
but of a blue tint in large masses. 

At 0° C. (32° F.) it crystallizes or freezes. At 100° C. (212° F.), 
and 760 millimetres (30 inches) barometric pressure, it is changed 
into an invisible colorless gas called steam, having the same elastic- 
ity as the air. Increased pressure raises the boiling-point, as does 
also the presence of solids in solution. "Water has its maximum 
density at 4° C. (39^-° F.), at which temperature one cubic foot 
weighs 997 ounces avoirdupois, and one American gallon 8^ lbs. 
One volume of water will produce 1320 volumes of steam at 100° C. 
and 760 millimetres barometric pressure. Water is the most uni- 
versal solvent known, nearly all substances being dissolved by it in 
greater or less degree. 

Hydrogen also forms one other compound with oxygen which 
deserves brief mention ; namely, hydrogen peroxide, H 2 2 . This is 
a liquid heavier than water, and was discovered by Thenard in 
1818. It begins to give off oxygen at 20° C, and at 100° C. is at 
once converted into water, giving off one-half the oxygen it con- 
tains. Half its oxygen appears to be very loosely held in the 
molecule, and is consequently very ready to unite with other oxi- 
dizable substances. On this account it has been proposed as a 
bleaching agent, and used as such with considerable success, but 
on account of the difficulty and expense attending its preparation 
on a large scale it has never come into extended use. 

It is somewhat employed for restoring old engravings. 

NITROGEN. 

Symbol, N.— Atomic weight, 1-4. — Molecule, N 2 . —Molecular weight, 28. 

Nitrogen, discovered in 1772 by Rutherford, is a gas without 

color, taste, or odor. It is lighter than air, its specific gravity 

being 0.972 compared to air, or 14 compared to hydrogen. Dry 

atmospheric air is a mixture of nitrogen with oxygen in the 



30 GENERAL CHEMISTRY. 

proportion of about four-fifths nitrogen and one-fifth oxygen by 
volume. Nitrogen is distinguished more for its negative than its 
positive qualities. It combines directly with but few of the 
elements, and, in these cases even, its combination is effected with 
considerable difficulty. Nitrogen is uninflammable. It is neither 
combustible in the air, like hydrogen, nor is it a supporter of 
combustion, like oxygen. 

Nitrogen may be easily obtained by passing air over red-hot 
copper, the oxygen of the air combining with the copper to form 
copper oxide, CuO, leaving the nitrogen practically pure. Only 
two compounds of nitrogen are of sufficient importance to be 
mentioned here, — ammonia and nitric acid. The former, nitrogen 
hydride or ammonia, NH 3 , is a colorless gas of strong pungent 
odor and totally irrespirable. It is very soluble in water and 
alcohol, water at 15° C. dissolving 727 times its own volume of 
the gas, forming the ammonia water (" stronger ammonia ") of 
commerce. A pressure of 6^ atmospheres condenses the gas at 
the ordinary temperature to a colorless liquid, which, when it is 
allowed to evaporate by the removal of the pressure, produces 
intense cold. This property of anhydrous liquid ammonia is 
taken advantage of in machines for producing ice. 

Ammonia is obtained in the incomplete combustion of organic 
substances containing nitrogen and hydrogen. It is obtained 
commercially as a by-product in the manufacture of bone char- 
coal and illuminating gas. Ammonia is a strong alkali, and as 
such receives many useful applications in the arts. 

Oxides of Nitrogen. 
Nitrogen forms five different compounds with oxygen, — 
N 2 0, N 2 2 , N 2 3 , X 2 4 , andN 2 5 . 

Only the last-mentioned, nitric anhydride, N 2 5 , is of interest in 
this connection. Nitric anhydride is a brilliant colorless crys- 
talline solid. When brought into the presence of water, H 2 0, it 
unites with it to form nitric acid, HN0 3 , according to the 
equation — ^ A + H 2 = 2 HN0 3 . 

Nitric acid, sometimes called " aqua f ortis," is a fuming corrosive 
liquid heavier than water. It boils at 85° C. and freezes at 
— 40° C. It stains the skin yellow and rapidly destroys its 



4 CARBON. 31 

substance. It unites with alkalis and metallic bases to form, for 
the most part, crystalline solids soluble in water, called nitrates. 
Potassium nitrate, KN0 3 , is "saltpetre," and sodium nitrate, 
NaN0 3 , is "Chili saltpetre." The latter is brought from Chili in 
large quantities, and forms the chief source of nitric acid. The 
acid is obtained from the nitrate by distilling the latter with 
sulphuric acid. Nitric acid acts energetically upon most of the 
metals, dissolving them to form nitrates. It transforms glycerine 
into nitro-glycerine and cellulose into guncotton. Gold and 
platinum are not affected by pure nitric acid, and iron is only 
attacked by the dilute acid, the strong acid so affecting the 
surface of iron as to render it what is called passive, and while in 
this state it entirely resists the action of the weaker acid. 

CARBON. 

Symbol, C. — Atomic Weight, 12. 

Pure carbon occurs in nature as the diamond. In this form it 
is usually colorless, of very high refractive power and great 
brilliancy when cut or polished. The diamond is the hardest of 
all known substances ; it does not conduct electricity and is incom- 
bustible at the highest heat attainable by the blowpipe. Heated 
in the voltaic arc, it swells up, takes the appearance of coke, 
becomes a conductor of electricity, and is slowly consumed. 

Graphite or plumbago is, so far as chemists have been able to 
determine, another natural form of pure carbon. Graphite occurs 
either massive or crystallized in six-sided plates, which have a 
metallic lustre. It is friable and almost greasy to the touch and 
leaves a black mark on paper — the mark of a common lead- 
pencil — although its ultimate particles are very hard. It is an 
excellent conductor of electricity. Graphite is frequently em- 
ployed in conjunction with grease as a lubricator for machinery. 
Lignite, stone coal, and coke are all more or less pure varieties of 
carbon. 

Lampblack is an artificial variety of nearly pure carbon. 

Compounds of Carbon. 

Carbon unites with hydrogen to form a long series of com- 
pounds — gaseous, liquid, and solid — called hydrocarbons, inter- 



32 GENERAL CHEMISTRY. 

esting examples of which are the gases, naphthas, and oils obtained 
from petroleum. These are all hydrocarbons, varying chemically 
only by the different numbers of carbon and hydrogen atoms 
which go to form the molecule in each. 

Carbon and Oxygen. 

Carbon unites with oxygen in two different proportions, form- 
ing carbon monoxide, CO, and carbonic anhydride or carbonic 
acid gas, C0 2 . The first product of combustion is always car- 
bonic anhydride, but when this subsequently passes over red-hot 
coals it gives up a portion of its oxygen and is reduced to the 
monoxide. Carbon monoxide is a colorless, odorless gas about as 
heavy as air. It is very poisonous when inhaled, and burns in the 
air with a blue flame, forming carbonic anhydride. The same 
product is formed when the monoxide comes in contact with 
metallic oxides, which give up their oxygen with production of 
the metal. The monoxide thus plays an important part in the 
operation of the blast furnaces used for smelting iron ore. When 
steam is passed over red-hot coals, carbon monoxide and hydrogen 
are formed. Together they constitute almost the entire portion of 
the so-called water-gas. 

Carbonic acid gas is also a colorless gas, one and a half times 
heavier than air. It has a faintly acid taste and odor. It some- 
times collects in mines, where it is called choke-damp. It is formed 
during the fermentation of liquids, and by its escape causes the 
effervescence noticed in such liquids. It is always present in small 
amount in the air, and cannot properly be called a poison, although 
it becomes injurious if breathed in excessive amount. Plants 
absorb it, retaining the carbon, which enters into their structure, 
and breathing out oxygen when in the sunlight. Animals reverse 
the process, absorbing oxygen and eliminating carbonic acid gas. 

Carbonic anhydride is uninflammable and does not support com- 
bustion, since it is already fully burned. Water at 15° C, and at 
the ordinary pressure, dissolves its own volume of the gas, and an 
additional volume for each 15 lbs. increase of pressure. Water so 
charged forms the ordinary soda-water. By a pressure of 38^ at- 
mospheres (38-| x 15 lbs.) at 0° C, the gas may be condensed to a 
colorless liquid, lighter than water, and may then be frozen, by its 
own evaporation, to a snow-like solid. Carbon dioxide, as it is also 



* CAHBON. 33 

called, is a product of the wet or dry combustion of all bodies con- 
taining carbon. It is evolved in large quantities from the kilns in 
which limestone is burned, and from the top of the limestone 
towers used in making sulphite liquor. 

In presence of water carbonic anhydride forms the true car- 
bonic acid, which unites with bases to form carbonates. Almost 
all the carbonates, except those of potassium, sodium, and ammo- 
nium, are nearly or quite insoluble in water, although rather soluble 
in water containing carbonic acid. Marble is nearly pure carbonate 
of calcium. All carbonates give off their carbonic acid with effer- 
vescence, on the addition of one of the stronger acids. 

Combustion. — All combustion, in the ordinary sense of the word, 
as already noted under Oxygen, is a process of combination with 
oxygen. In the pure gas such combination, once started, proceeds 
with uncontrollable energy until the combustible body is consumed ; 
but in ordinary cases the supply of oxygen is drawn from the 
atmosphere, where one-quarter by weight of oxygen is diluted with 
three-quarters of inert nitrogen. The following reactions serve to 
illustrate the more typical cases of combustion, and indicate the 
resulting products : — 

Combustion of hydrogen . . . 2 H, + 0, = 2 H 2 

" of carbon (charcoal) C + 0, = C0 2 

of marsh gas . . CH 4 +2 2 = C0 2 + 2 H 2 

of -alcohol . '. . . C 2 H 5 (3H + 3 0, = 2 C0 2 + 3 HoO 

" of sulphur . . . S 2 + 2 2 = 2 S0 2 

" of phosphorus . . P 4 + 5 2 = 2 P 2 5 

The ordinary combustibles, like coal, wood, petroleum, and illu- 
minating gas, are compounds of carbon and hydrogen, and form by 
their burning carbonic acid gas and water. The light and heat 
developed during combustion are due to the rushing together of 
the atoms under the attractive force of chemical affinity. The 
amount of heat developed varies greatly with different combusti- 
bles, and depends upon the kind of atoms composing their molecules, 
and the extent to which the affinities of these atoms are already 
satisfied. The number of heat units developed by the combus- 
tion of one kilogramme of several different substances is given 
on the following page : — 



34 



GENERAL CHEMISTRY. 



Hydrogen 34462 

Alcohol . . . 7184 

Sulphur 2221 

Charcoal 8080 

Dry wood . 3654 

Soft coal 7500 

Gas coke 8047 

If a flame like that of an ordinary candle is inspected closely, 
the existence of three distinct zones, as shown in Figure 1, may 
be detected. The innermost, dark zone, consists of 
gas formed by heat from the melted wax drawn up 
by the capillary action of the wick. The two outer 
zones shut off the inner one from the oxygen of the 
air, and there is consequently no combustion within 
this zone. The middle zone is the one from which 
most of the light is derived. There is here not suffi- 
cient air for complete combustion, and the minute 
particles of carbon are rendered incandescent by the 
heat. The flame at this point is a reducing one, 
because the white-hot carbon and partially burned 
gases possess so strong an affinity for oxygen that 
many metallic oxides give up their oxygen and are 
reduced to the metal if this portion of the flame is brought to bear 
upon them. The carbon and gases are completely burned to C0 2 
and H 2 in the outer zone, in which, of course, an excess of oxygen 
is present ; and the action of the flame at this point is an oxidizing 
one, since conditions are favorable for the oxidation of a metal 
brought within it. 

Carbon unites with both oxygen and hydrogen to form a large 
class of organic substances called carbohydrates, of which sugar, 
C12H22O11, starch, and cellulose (C H 10 O 5 ) n , are notable examples. 
Many of these substances, as, for instance, starch and cellulose, 
have the same number of the elementary atoms in the molecule, so 
that their percentage composition, or the proportion of C, H, and O, 
is the same in each. In these cases the different character of the 
substances is supposed to be due to a different arrangement of the 
several atoms in the individual molecule. 

Many of the carbohydrates are valuable food substances, being 
burned in the system by means of the oxygen inhaled, and furnish- 
ing fuel, so to speak, for the fires of life. Any superabundance 




Fig. 1. 



SULPHUR. 



above what may be required for keeping up the animal heat and 
energy is either voided unchanged or is transformed into fat and 
stored as such in the body, according to the vigor of the individual 
system. The number of the various compounds in the organic world 
into which carbon enters is almost infinite, and the study of the 
carbon compounds, or organic chemistry, forms a science in itself. 
Probably no other element, if we except oxygen, takes part in 
the formation of such a variety of compounds of the highest use to 
man as carbon. 

Carbon and Nitrogen. 

When air is passed over potassium carbonate mixed with char- 
coal, and contained in a red-hot tube, the nitrogen of the air unites 
with carbon to produce a colorless and extremely poisonous gas, 
called cyanogen, C 2 N 3 , which has the odor of peach blossoms or 
bitter almonds. Cyanogen is 1.8 times as heavy as air. It is 
easily condensed by cold and pressure into a colorless liquid. 
Water dissolves four times its volume of the gas. When heated 
in the air cyanogen burns with a beautiful pink flame, producing 
carbon dioxide and free nitrogen. Cyanogen unites directly with 
hydrogen to form cyanhydric or " Prussic " acid, CNH, a colorless 
transparent liquid most intensely poisonous. When inhaled, even 
in very minute quantities, it produces headache, giddiness, etc. 
The hydrogen in prussic acid may be replaced by metals to form 
cyanides. Cyanogen, under certain conditions, may be made to 
unite with iron and potassium to form ferrocyanide and ferricyanide 
of potassium. 

The ferricyanide of potassium is red, and is commonly known 
as red prussiate of potash. Its solutions, when mixed with those 
of ferrous salts (see Iron), yield a blue precipitate. Ferrocyanide 
of potassium, or yellow prussiate of potash, occurs in beautiful 
yellow crystals. It gives a white precipitate with ferrous salts, 
which turns blue on exposure to the air. With ferric salts, which 
contain more oxygen, the precipitate is the ordinary Prussian 
blue. 

SULPHUR. 

Symbol, S. — Atomic weight, 32. — Molecule, S 2 . — Molecular weight, 64. 

Sulphur is a pale-yellow, brittle solid of specific gravity 2.045. 
It occurs native in Sicily, and on the shores of the Mediterranean 



36 GENERAL CHEMISTRY. 



Sea, in Japan, and in Utah, and some other parts of the western 
portions of the United States. The principal commercial source of 
sulphur is Sicily, though considerable quantities reach the Pacific 
coast from Japan, and an occasional cargo of Japanese sulphur may 
be found in New York. The deposits in our own country, although 
very extensive and of high-grade ore, remain at present in an unde- 
veloped condition. In Sicily the sulphur is found mixed with 
earth, and to prepare it for export large heaps of the sulphur-bear- 
ing earth are formed around a central opening and covered with 
turf, air channels being left near the bottom of the heaps. Some 
brushwood is laid at the bottom in building the heap. When the 
mound is finished the brushwood is fired, and the heat from this 
melts a portion of the sulphur, which runs toward the central hole, 
and there accumulates, to be drawn off from time to time into pans, 
where it is allowed to cool. Only a small quantity of wood is used 
to start the heap, since as soon as the sulphur begins to melt a 
portion of it is ignited and serves to heat the pile. The amount of 
air admitted through the air channels is carefully regulated so as 
only to allow enough sulphur to be burned to keep up the very 
moderate heat required. 

In England considerable quantities of sulphur are now being 
recovered by the Chance process, in an almost chemically pure 
state, as a by-product in the Leblanc process of soda manufacture. 
Chance treats the waste sulphide of calcium with carbonic acid to 
expel the sulphur as sulphuretted hydrogen, H 2 S. By carefully 
regulating the supply of air this is then burned in accordance with 

the reaction — 

H 2 S + = H 2 + S 

into watery vapor and sulphur. 

Sulphur melts at 114° C. (238° F.) to a thin, amber-colored fluid. 
On further heating, the liquid thickens and turns dark, until at 
about 240° C. it is very nearly black, and so thick and tenacious 
that the vessel containing it may be inverted without the sulphur 
running out. At a still higher temperature it again forms a thin 
liquid, and at 446° C. boils and gives off vapors or sublimes. This 
sulphur vapor, when condensed or sublimed, forms a fine crystalline 
powder, known in pharmacy as " Flower " or Flowers of Sulphur. 

Native sulphur is found crystallized in the form of octahedrons, 
and when crystallized from solution in carbon disulphide, sulphur 
always takes this form. When, however, sulphur is melted and 



SULPHUR. 37 



allowed to cool, it crystallizes in the form of oblique prisms, having 
a specific gravity of 1.98. 

A third modification of sulphur appears when that substance, at 
a temperature of about 250° C, or in the second liquid stage, is 
poured slowly into water. It then appears as an elastic ductile- 
solid, soft and resembling in a marked degree crude caoutchouc or 
rubber. On exposure to the air, however, this modified sulphur 
soon loses its amorphous form, and returns to the ordinary pris- 
matic variety. 

Sulphur is insoluble in water, and only very slightly soluble in 
alcohol. It is somewhat more soluble in ether and the essential 
oils generally, and in petroleum naphtha. It is abundantly soluble 
in carbon disulphide, CS 2 ; in sulphur dichloride, S 2 C1 2 ; benzene, 
coal-tar naphtha, C 6 H 6 ; and in boiling turpentine spirit, C 10 H 16 . 

Sulphur burns readily in the air, with a beautiful blue flame, 
producing sulphur dioxide, S0 2 , sulphurous acid gas. 

Four qualities of sulphur are recognized by the trade. " Firsts " 
consist of large, shining pieces of amber color ; " seconds " are not 
so shining, but are still purely yellow ; " thirds " are of a dirtier 
color, often inclining to red or brown, and both these latter qualities 
contain much powder. " Recovered " sulphur, so called from its 
method of preparation from alkali waste, is equal in color to firsts 
and contains only a trace of impurity. Unlike the other grades, 
which, are shipped in bulk, recovered sulphur is usually shipped in 
bags. The total ash of commercial Sicily sulphur is rarely over 
2 per cent., and often only 0.5 per cent. 

Compounds of Sulphur. 
SULPHIDES. 

Sulphur unites directty Avith most of the metals, when heated 
with them, to form sulphides. Copper, for example, when heated 
to redness in vapor of sulphur, unites with the latter to form 
copper sulphide, CuS. Many of the sulphides of the metals are 
found in nature, and sometimes, as in the case of lead sulphide, 
galena, PbS, and mercury sulphide, cinnabar, HgS, form the most 
valuable ores of the metals. Iron pyrites, FeS 2 , and copper pyrites, 
FeCuS 2 , are valuable minerals, both for the sulphur they contain 
and also for their metal. Both minerals occur as golden-yellow 



GENERAL CHEMISTRY. 



masses, or crystalline grains, so often mistaken for gold that they 
have received the name of " Fool's gold.'' By roasting iron pyrites 
and many other native sulphides, Avith free access of air, all the 
sulphur may be burned out of the mineral, going off as sulphurous 
acid gas, S0 2 , which may be utilized for various purposes, as the 
making of " sulphite liquors " for the manufacture of sulphite pulp, 
etc. Iron pyrites, often containing more or less copper, is the 
sulphide usually chosen for this purpose on account of its larger 
content of sulphur than many others, and of the ease and complete- 
ness with which the sulphur may be burned out in a properly con- 
structed furnace. 

Most of the native sulphides are insoluble in dilute acids. When, 
however, artificially prepared sulphides, as sulphide of iron, FeS, 
are treated with dilute hydrochloric or sulphuric acid, HC1, or 
H 2 S0 4 , the metal is dissolved to form a metallic chloride or sul- 
phate, while the sulphur of the sulphide and the hydrogen of the 
acid are simultaneously freed from the former combinations, and 
unite to form hydrogen sulphide, sulphuretted hydrogen, H. 2 S. 
Sulphur and hydrogen combine directly only when both are in 
what is called the nascent condition ; that is, at the instant of their 
liberation from some previous combination. 

Nearly all the sulphur which abroad enters into the manufacture 
of sulphuric acid is derived from iron pyrites, containing more or 
less copper, and usually a small amount of arsenic. Pyrites furnish 
the cheapest source of sulphur, but require for their burning a 
much more elaborate and expensive plant than the element itself, 
and a considerable quantity of fine brown dust is carried along with 
the gas. For these reasons sulphur has usually been preferred by 
sulphite mills, although in a few instances pyrites have been intro- 
duced. The content of sulphur in the different ores varies from 27 
to about 50 per cent., good ores usually carrying about 45 per cent. 

Hydrogen Sulphide, KLS, is a colorless gas of an extremely of- 
fensive odor. It possesses narcotic properties. It is somewhat 
heavier than air. Water dissolves, at the ordinary temperature, a 
little more than three times its volume of the gas. By a pressure 
of 17 atmospheres H 2 S may be condensed to a liquid. It is usually 
formed in the decay or putrefaction of organic substances which 
contain sulphur, either in their own composition or that of. a com- 
pound of sulphur mixed with them. This fact explains the fetid 
odor sometimes noticed in sulphite pulp, or soda pulp, which has 



SULPHUR. 39 



been allowed to remain in the drainers or other un ventilated place 
for some time before it is properly washed. In both cases the 
liquors left in the pulp contain compounds of sulphur, and the 
commencing decay of organic substances in the pulp, or of the pulp 
itself, begets a change in the sulphur compound, which results 
in the production of H 2 S. The darkened color of such ill-smelling 
pulp maybe accounted for in two ways, either by the presence in the 
solution of traces of metals which would be transformed into black 
sulphides by the H 2 S formed, or the presence of organic matters in 
the pulp, other than cellulose, may determine the decomposition 
of a portion of the H 2 S formed with the production of a dark color 
by the precipitation of free sulphur. Pure cellulose is not dark- 
ened by H 2 S, but if left in contact with H 2 S, in the presence of air, 
for any considerable time, sulphur is precipitated in it by the 
decomposition of the H 2 S, and it takes on a more or less dark color. 
Hydrogen sulphide, or sulphuretted hydrogen, burns with a blue 
flame to. form water and sulphurous acid gas. It forms one of 
the most valuable reagents to the analyst, as by its aid he is able to 
separate the common metals from all other substances. 



Sulphur and Oxygen. 

Sulphur unites with oxygen in a great variety of proportions to 
form oxides of sulphur, or, as they are termed, sulphur anhydrides, 
which in turn unite with the elements of water to form sulphur 
acids, or with metallic oxides to form sulphur salts. The follow- 
ing is a list of the various oxides of sulphur, with their correspond- 
ing acids : — 

SO + H 2 = H. 2 S0 2 .... Hyposulpliurous acid. 

50 2 + H 2 = H0SO3 .... Sulphurous acid. 
S 2 2 + H 2 = H 2 S 2 3 .... Thiosulphuric acid. 1 

50 3 + H 2 = H 2 S0 4 .... Sulphuric acid. 
S 2 4 + H 2 = H 2 S 2 5 .... Di-thionic acid. 
S 3 4 + H 2 =-- H 2 S 3 5 .... Tri-thionic acid. 
S 4 4 + H 2 = H 2 S 4 5 .... Tetra-thionic acid. 
S 5 4 + H 2 = H 2 S 5 5 . . . Penta-thionic acid. 

1 Often improperly called hyposulpliurous acid. 



40 GENERAL CHEMISTRY. 

Only the first four of these are of common occurrence or use in 
the arts. These we will consider in the natural order of their 
manufacture from sulphur. When sulphur is burned with free 
access of air, it combines with oxygen, as we have already said, to 
form sulphur dioxide, S0 2 , called sulphurous anhydride, or sul- 
phurous acid gas. This is the starting-point for the manufacture 
of all the oxygen compounds of sulphur. Either sulphur may be 
used or pyrites, which gives up its sulphur as S0 2 on heating in air. 
When the latter is employed as the source of sulphur, a furnace for 
burning it must be used, in which more or less elaborate mechanical 
appliances are necessary to facilitate the handling of the ore and 
the removal of the burned cinder, called " Blue Billy." In the 
burning of sulphur only the simplest appliances are necessary. A 
furnace as satisfactory as any for this purpose consists simply of a 
cast-iron retort, with a flat bottom and arched top, one end being- 
open, and a pipe leading from the crown of the arch near the 
closed end for the escape of the S0 2 formed. The front, or open 
end, is fitted with a sliding iron door, which may be raised or 
lowered to regulate the admission of air. The sulphur is fed in 
through this door on to the bottom of the retort, and once ignited 
needs no other fuel to keep it burning. Water is allowed to 
trickle continuously upon the top of the retort in order to keep 
the heat below the boiling-point of sulphur, and prevent its " sub- 
liming," or going away in vapor without burning, as in this event 
it would be deposited in the cooler portions of the pipes, to cause 
trouble by clogging. In the manufacture of " sulphite liquor " for 
reducing wood, the gas is usually led through tanks containing 
milk of lime or magnesia, as will be described under the Sulphite 
Pulp Process, which see. 

Sulphurous acid gas, S0 2 , properly called sulphurous anhydride 
("without water"), is a colorless, pungent, suffocating gas, of a 
specific gravity, compared with air, of 2.21. So long as sulphurous 
anhydride is kept from contact with moisture, it remains an inert 
gas, having no effect upon metals or other dry substances with 
which it may come in contact. 

Sulphurous anhydride may be readily prepared for laboratory 
experiments by heating metallic copper Avith strong sulphuric acid. 
The reaction is represented by the equation — 

Cu + 2 H,S0 4 = CuS0 4 .+ H,0 + S0 2 . 



THE SULPHITES. 41 



Water at 0° C. will absorb 79.8 times its volume of S0 2 , and 39.4 
times its own volume at 20° C. Sulphurous anhydride is .con- 
densed into a liquid b}^ a temperature of — 17.8° C, and by increased 
pressure it may be liquefied at considerably higher temperatures. 
Liquid S0 2 may be obtained in syphons similar to those in which 
Seltzer and other carbonated waters are sold. 

Sulphurous anhydride combines with one molecule of water to 
form sulphurous acid, H 2 S0 3 , as before shown on page 39, and then 
becomes an extremely active substance. It attacks and rapidly 
corrodes most of the metals, dissolving or combining with them to 
form sulphites. Copper, zinc, tin, aluminum, and iron are rapidly 
eaten away by solutions of sulphurous acid. Lead, however, and 
alloys of that metal with antimony resist its action almost entirely. 
Certain alloys, in which copper forms the greater part of the metal, 
resist the action of sulphurous acid to a very considerable extent. 
All of them, however, yield to the action of the acid more or less 
rapidly. 

Sulphurous acid is able to decompose the oxides, hydrates, and 
carbonates of the alkali metals, and metals of the alkaline earths 
forming sulphites of the metals, and water, in the case of the oxides 
and hydrates ; and sulphites of the metals, water and carbonic acid 
in case of the carbonates, thus : — 

Na 2 + H 2 S0 3 = Na 2 SO s + H 2 ; 
2 NaHO + H 2 S0 3 = Na 2 S0 3 + 2 H,0 ; 
!N T a,C0 3 + H,S0 3 = Na 2 S0 3 + H,0 + C0 2 ; 
CaO +H 2 S0 3 = CaS0 3 + H 2 Q; 
CaG0 3 +'H s S0 8 = CaS0 8 +H 2 + C0 2 . 

Bisulphites, preferably called Acid Sulphites. — Sulphurous 
acid, H 2 S0 3 , like all the oxygen acids of sulphur, is a bibasic acid; 
that is, it contains two atoms of basic hydrogen, or hydrogen so situ- 
ated with reference to the other atoms in the molecule that it may 
be replaced by an equal number of atoms of a univalent alkali metal 
as sodium, or by a single atom of a bivalent alkaline earth metal, as 
calcium or magnesium. There are, in consequence, two series of 
sulphites, the neutral or normal, or monosulphites, mentioned in 
the preceding paragraph, in which compounds both the hydrogen 
atoms are replaced by a metal, and the bisulphites, or acid sulphites, 
in which only one of the hydrogen atoms in the molecule of acid is 



Soc 


Hum bisulphite. 


H 


-0 X 





Calc 


ium bisulphite. 


H 


s= 

/ 





Ca 


\ 




H 








42 GENERAL CHEMISTRY. 

replaced by a metal. The bisulphites therefore retain much more 
of the acid character than do the normal sulphites. This difference 
in the structure of the two molecules may be shown thus : — 

Normal sodium sulphite. 

Na-O v 
Na - x 

Normal calcium sulphite. 

Ca' /S = 

Sulphurous acid. 

H-Ox 

;s=o 

H-0 / 

The contracted or empirical formula of the bisulphites named is 
for sodium bisulphite, HNaS0 3 ; for calcium bisulphite, H 2 CaS 2 6 . 
It will be noticed that, because calcium is a bivalent metal, two 
molecules of sulphurous acid unite with one atom of calcium in 
forming the bisulphite. 

The bisulphites are formed when only sufficient of the base is 
added to a solution of sulphurous acid to half neutralize the acid, 
or more commonly in practice, as in the manufacture of sulphite 
liquors, by first bringing sufficient acid into contact ivith the base 
to form the normal sulphite, and then continuing the addition of 
sulphurous acid until the normal sulphite is converted into the 
bisulphite. They may also be formed by adding to the normal 
sulphite enough of a stronger acid than sulphurous to displace one- 
half the sulphurous acid, thus : — 

c , . . . , , Sodium sulphite ,. „,. , . , Sodium bisulphit 

Sulphuric acid + (2 mo iecules) = Sodium sulphate + (2 mo i e cule 6 ). 

H 2 S0 4 + 2 Na 2 S0 3 = Na 2 S0 4 + 2HNaS0 3 . 

A similar reaction takes place, to some extent, in sulphite 
digesters, when, during the boiling operation, a portion of the 
sulphurous acid is oxidized to sulphuric acid ; although, if the 
sulphite liquor contains only bisulphite at the start, the sulphurous 
acid displaced appears as free sulphurous acid, and increases the 
gas pressure. 

The acid sulphites (bisulphites) of the alkaline earth metals are 
what are called loose or unstable chemical compounds, being easily 



THE SULPHITES. 48 



broken up or decomposed into the neutral salt and free acid by 
heat alone ; the acid being volatilized. Acid sulphite of magne- 
sium is less easily decomposed than the corresponding calcium salt, 
but both are so unstable that their solutions cannot be evaporated 
without decomposing the salt. Neither of these salts has been 
isolated, and indeed many good authorities hold the opinion that 
acid sulphites of the alkaline earth metals do not exist, the so-called 
bisulphite solutions of these bases being simply solutions of the 
neutral sulphite in aqueous sulphurous acid. Certain facts in our 
own experience with, these solutions, however, make us strongly 
of the opinion that these salts are formed and do exist in the so- 
called bisulphite solutions. Certainly there is no theoretical reason 
why they may not be formed. 

The acid sulphites of the alkali metals are definite compounds, 
and can be crystallized from their solutions. Both the neutral and 
acid sulphites of the alkali metals are very soluble in water. 
Neutral sulphite of magnesia is much less soluble, while that of 
calcium is nearly insoluble. Neutral sulphite of magnesium sepa- 
rates from solution in coarse, sandy crystals, while that of calcium, 
forms a fine, granular precipitate Avhen S0 2 gas is passed into lime- 
water. It often forms coral-like crusts on the containing vessels, 
and, when precipitated by heat from the solution of the acid sul- 
phite, often concretes in hard, stony masses. It frequently appears 
in the bottom and on the sides of digesters used for " cooking " 
wood with bisulphite of lime, sometimes forming a scale an inch or 
more in thickness. 

All the bi- or acid sulphites appear to be soluble in water. The 
addition of any of the stronger acids to a sulphite causes the libera- 
tion of S0 2 , often with effervescence. The acid sulphites form 
soluble, and many of them crystallizable, compounds with certain 
organic substances called aldehydes and ketones, and to this fact is 
probably due, in part at least, their efficiency in reducing wood to 
fibre. 

Sulphurous acid, both free and in combination, is very ready to 
take on more oxygen and be changed into sulphuric acid. Hence 
it is called a reducing agent, since it can reduce certain other com- 
pounds from a higher to a lower state of oxidation, being itself, at 
the same time, oxidized. This property gives it its value as an 
antichlor, it being more easily oxidized by the " bleach " than is the 
fibre. 



44 GENERAL CHEMISTRY. 



This reducing action is of first importance in the sulphite process 
for making pulp, since, on account of it, any oxidation and con- 
sequent weakening of the fibre is prevented, while the incrusting 
matters of the wood are so little changed by the process of solution 
that there is good reason to believe that they may be made to yield 
valuable by-products. 

Sulphurous acid also possesses marked bleaching power, which 
depends on the fact that the acid forms colorless compounds with 
the coloring-matter. These compounds may often be broken up, 
and the color restored, by treatment with alkali. The sulphurous 
acid bleach is not a permanent one, like that obtained by the use 
of hypochlorites, which destroy the coloring-matter. The acid is 
used for bleaching wool and straw. It also gives a fictitious color 
to sulphite pulp. Such pulp, after washing, is often as white as it 
is after bleaching with bleaching-powder, although this first color 
is not very permanent. 

The moist gas and also the sulphites and bisulphites are very 
destructive to the lower forms of life, preventing fermentation and 
destroying disease germs. They are much employed as disinfec- 
tants. 

Hyposulphurous Acid, H 2 S0 2 . — When aqueous sulphurous 
acid is poured upon zinc, best in the shape of clippings or zinc 
dust, the metal dissolves, but no hydrogen is evolved. The nascent 
hydrogen formed combines at once with an atom of oxygen, which 
it takes from the molecule of sulphurous acid, with formation of 
hyposulphurous acid and water. Thus — 

H 2 S0 3 + H 2 = H 2 S0 2 + H 2 0. 

When the zinc is added to a solution of a bisulphite, as, for 
instance, bisulphite of soda, the reaction is as follows : — 

3 NaHS0 3 + Zn = XaHSO, ( hJ ' p ;£ ite ) + Na 2 S0 3 + ZnS0 3 + H 2 0. 

Hyposulphurous acid has never been isolated. It is produced in 
the decomposition of sulphurous acid by the electric current, but 
is such an unstable compound that it reoxidizes to sulphurous acid 
almost immediately. All its salts are very unstable, contact with 
the air very rapidly changing them, through absorption of oxygen, 
to the acid sulphites. The hyposulphites are extremely power- 
ful reducing agents ; that is, they act powerfully in withdrawing 



SULPHURIC ACID. 45 



oxygen from other compounds of this element, reducing them to a 
lower state of oxidation. They are even capable of reducing indigo 
to the soluble and colorless form, and have been commercially 
applied for this purpose. 

Calcium hyposulphite is the salt usually chosen for this purpose 
on account of the comparative ease of its preparation, and because 
it is the most stable in solution of these compounds. Only one of 
the hyposulphites has been obtained in the solid, or crystallized, 
form ; namely, sodium hyposulphite. This salt may, by the exer- 
cise of great care in the manipulation of a somewhat lengthy proc- 
ess, be crystallized from its alcoholic solution, and may be pre- 
served for some time, if carefully kept from contact with the air. 

Thiosulplmric Acid, H 2 S 2 3 . — ■ This acid is, like the preceding, 
not known in the free state ; any attempt to separate it from one 
of its salts resulting in the breaking up of the acid into sulphurous 
acid and free sulphur, which is precipitated. The only one of 
its salts which possesses any interest is sodium thiosulphate, 
Na 2 S 2 3 , 5 H 2 0, the commercial name for which is '-hyposulphite of 
soda." This salt is largely used in photography, and also in 
bleacheries as an " antichlor " to destroy any trace of " bleaching 
chlorine " remaining in the bleached material. Its use for the 
latter purpose is, however, to be discountenanced in favor of the 
sulphites, since the former leaves free sulphur in the fabric by its 
decomposition, which is liable to work injury, while the sulphites 
are merely changed to comparatively harmless sulphates. 

Thiosulphate of sodium is easily prepared by heating a solution of 
sodium sulphite for some time with powdered sulphur, evaporating 
the solution and crystallizing out the salt. It forms large, color- 
less crystals readily soluble in water, and of a cooling saline and 
sulphurous taste. 

The crystals contain five molecules (5 H 2 0) of water of crystal- 
lization. 

Sulphuric Acid, H 2 S0 4 ; commercial name, "Oil of Vitriol." 
— This acid probably holds the place of highest importance in the 
arts of any known acids. It is formed from sulphurous acid by the 
addition of an atom of oxygen to the molecule of the latter, 

H 2 S0 3 +0 = H 2 S0 4 . 

This is always accomplished slowly, by natural means, whenever 
sulphurous acid is exposed to the action of atmospheric oxygen. 



46 GENERAL CHEMISTRY. 

The first step in the manufacture of sulphuric acid is always the 
burning of sulphur (generally in pyrites) into sulphurous anhy- 
dride, and its combination with moisture into sulphurous acid. 
The rapid oxidation of the latter into sulphuric acid is accom- 
plished by the aid of nitrous fumes, produced by heating nitre ; 
oxygen from the air, and steam. Sulphurous anhydride from 
burning sulphur, nitrous fumes, steam, and air are introduced 
together into large chambers made of 7 lb. sheet lead. 

The entire course of the reactions which take place in the cham- 
bers is not definitely known. A very small amount of the nitrous 
fumes is, however, found to be sufficient to cause an almost un- 
limited amount of H 2 S0 3 to be oxidized to H 2 S0 4 , the nitrous 
fumes, which consist of a mixture of several oxides of nitrogen, 
apparently acting simply as carriers of oxygen, alternately giving 
up a portion of their oxygen to the sulphurous acid, and renewing 
their supply from the air present in the chamber. The H 2 S0 4 , as 
it is formed, falls as a fine rain, and collects on the floor of the 
chamber, diluted with the condensed water from the excess of 
steam always present in the chamber. This dilute acid is known 
as " chamber acid," and usually contains about 50 to 60 per cent, of 
real H 2 S0 4 . 

This chamber acid may be concentrated to a gravity of about 1.78, 
and containing about 70 per cent, of H 2 S0 4 , by evaporation in leaden 
pans, when it is technically called B. O. V. (brown oil of vitriol). 
Beyond this point the acid begins to attack the lead, and must then 
be further concentrated in vessels of glass or platinum. The 
metal is most used on account of the liability of glass to breakage 
and the disastrous effects of the acid when this occurs. The con- 
centration may be continued until oil of vitriol is obtained, having 
a gravity of 1.84, a boiling-point of 338° C, and containing 100 per 
cent. H 2 S0 4 . 

Sulphuric acid, H 2 S0 4 , is a colorless and odorless, heavy liquid, 
of an oily appearance. It freezes at — 26° C. It chars wood and 
other organic bodies. It has a great affinity for water, absorbing 
more than its own volume from the air when exposed for some 
time. A very dilute solution of H 2 S0 4 has the property of chang- 
ing cellulose and starch into glucose when heated with them for 
some hours, and more rapidly under high pressures. Sulphuric 
acid of 1.60 specific gravit}^ will, at a temperature of 50° C, dis- 
solve cellulose, without charring, to a nearly colorless solution, 



SULPHURIC ACID. 4T 



which may be diluted with water without precipitation. This 
property of the acid furnishes an easy method for the estimation 
of total cellulose compounds in woody materials, since the non- 
cellulose compounds are neither charred nor dissolved by acid of 
the above strength. 

Sulphuric acid unites with bases to form sulphates, all of which 
are soluble in water except the sulphates of barium, strontium, and 
lead. Sulphate of lime is only moderately soluble, one part of the 
crystallized salt, CaS0 4 , 2 H 2 0, requiring 400 parts of water at 
15° C. for solution. 

Quite a number of sulphates are of natural occurrence, as heavy 
spar (barium sulphate, BaS0 4 ), gypsum (calcium sulphate, 
CaS0 4 , 2 H 2 0),celestine (strontium sulphate, SrS0 4 ), and Epsom 
salts (magnesium sulphate, MgS0 4 , 7 H 2 0). 

" Nordhausen," or fuming, sulphuric acid, which is H 2 S0 4 , con- 
taining sulphurous anhydride, S0 3 , is obtained by distilling dry 
ferrous sulphate (copperas), FeS0 4 . It is useful as a solvent for 
indigo blue, and is mainly consumed in the manufacture of indigo 
extracts, carmines, etc. 

Sulphuric anhydride, S0 3 , may be obtained pure, as a mass of 
white, silky needles, by passing S0 2 and O through a red-hot 
porcelain tube filled with spongy platinum, and condensing the 
vapors in an air-tight receiver, surrounded with ice. 

Solid S0 3 has a specific gravity of 1.946. It melts at 18.8° C, 
and boils at 35° C. When thrown into water it hisses like a red- 
hot iron, and dissolves, forming H 2 S0 4 . S0 3 is soluble in all pro- 
portions in pure H 2 S0 4 . 

The remaining acids of sulphur — namely, the di-, tri-, tetra-, and 
penta- thionic acids — and their salts are of no commercial value. 
They are all unstable acids, which are known only in combination. 
None of them have been obtained in the free state. They are 
formed to some extent, in the sulphite process, through the action 
of sulphurous acid upon sulphur vapor when overheating of the 
furnace occurs. The dithionates decompose on heating into S0 2 
and a sulphate, but the decomposition of the higher sulphur acids 
is attended with separation of sulphur, and their presence in sul- 
phite liquors is, on this account, very objectionable. 



48 GENERAL CHEMISTRT. 



/Sulphur and Nitrogen. 

Sulphur forms a single compound with nitrogen, S 2 N 2 , obtained 
by passing dry ammonia gas through a solution of sulphur di- 
chloride, S 2 C1 2 , in carbon disulphide. It forms golden-yellow 
crystals, insoluble in water. It explodes when heated to 157° C. 
Of no practical interest. 

Sulphur and Carbon. 

When vapor of sulphur is passed over red-hot charcoal, the two 
combine to form carbonic sulphide, or carbon bisulphide, CS 2 . 
This is a colorless, very inflammable liquid, of specific gravity 1.66, 
boiling at 83° C. It has a very high refracting power. When 
pure, CS 2 has a not unpleasant ethereal odor : but, as usually met 
with, it possesses a very repulsive odor, reminding one of rotten 
cabbage. 

Bisulphide of carbon is of considerable importance in the arts as 
a solvent of sulphur, phosphorus, iodine, and rubber or caout- 
chouc. It is also a free solvent of fats and oils, and is employed 
in the manufacture of certain acid-proof paints from asphalt, and 
petroleum residues. 

SELENIUM. 

Symbol, Se. — Atomic weight, 79.5. — Molecule, Se 2 . — Molecular weight, 159. 

Selenium is a reddish-brown solid, of specific gravity 4.3. It 
melts above 100° C, and boils at 343° C. When heated in the air, it 
has an extremely disagreeable odor of decayed horseradish. In its 
properties and combinations selenium presents a very close analogy 
to sulphur. Selenium has never been found native. It was dis- 
covered by Berzelius in 1817. It is of no importance in the arts. 

TELLURIUM. 

Symbol, Te. — Atomic weight, 128. — Molecule, Te 2 . — Molecular weight, 256. 

This substance also presents a close analogy to sulphur, but in 
appearance approaches very closely to the metals, being lustrous 
like silver. The specific gravity of Te is 6.26. It melts below a 
red heat. It occurs rarely native in Hungary, but chiefly in com- 
bination with other metals as Tellurides. Both selenium and 



CHLORINE. 49 



tellurium often occur in Japanese sulphur. Tellurium was first 
discovered by Miiller in 1782. Like selenium it is of no com- 
mercial importance. 

CHLORINE. 

Symbol, CI. — Atomic weight, 35.5. — Molecule, Cl 2 . — Molecular weight, 71. 

Chlorine is a yellowish-green gas of specific gravity 2.47 com- 
pared with air. It is uninflammable and irrespirable. Water at 
the ordinary temperature, 15° C, dissolves 2.3 times its own volume 
of the gas; it also combines with water at 0°C. to form a solid 
crystalline hydrate of chlorine, Cl 2 , 10 H 2 0. A pressure of 90 lbs. 
at a temperature of 0° C. condenses the gaseous chlorine into a 
yellow liquid 1.33 times as heavy as water. 

Chlorine was discovered by Scheele in 1774. It never occurs 
native, but always in combination Avith abase as a metallic chloride. 

Sea- water contains the chlorides of potassium, sodium, calcium, 
and magnesium, each in considerable amount. Chlorine has a very 
strong affinity for the metals generally. Many of them when 
placed, in a finely divided condition, in an atmosphere of chlorine, 
combine with it so rapidly as to be raised to vivid incandescence by 
the heat of the chemical action. It also has a great affinity for 
hydrogen, with which it combines to form hydrochloric acid, HC1. 
Many hydrogen compounds are at once decomposed by chlorine in 
solution with the formation of HC1 and free oxygen. Chlorine is 
a powerful disinfecting and bleaching agent, in the presence of 
light and moisture. Its effect, in these instances, is explained by 
its decomposition of water, when the liberated oxygen destroys the 
identity of the disease germs in the one case, or the coloring- 
matter in the other. It may be termed a powerful secondary 
oxidizing agent, since, though not itself an oxidizer, it produces an 
oxidizing action through the agency of the elements of water. 

Chlorine and Hydrogen. 

Hydrochloric Acid. — Chlorine, as already stated, is eager 
to combine with hydrogen, atom for atom, both being univalent, 
forming chloride of hydrogen, or hydrochloric, commercially called 
muriatic, acid, HC1. 

This is a colorless, incombustible gas, of specific gravity, com- 



50 GENERAL CHEMISTRY. 

pared with air, of 1.27. It is of intensely acid taste, and pungent, 
irritating odor. It may be condensed by a pressure of 40 atmos- 
pheres, at 10° C, to a colorless liquid. The hydrochloric or 
muriatic acid of commerce is, however, merely a solution of the gas 
in water, which will dissolve, at 0° C, 500 times its own volume of 
the gas. Ordinary muriatic acid is yellow from the presence of 
chloride of iron, and it frequently also contains some sulphuric 
acid. Pure hydrochloric acid is colorless, and if evaporated on a 
piece of glass or porcelain leaves no residue. Hydrochloric acid is 
prepared commercially by treating chloride of sodium, common 
salt, with sulphuric acid, the torrents of hydrochloric acid which 
are given off being a by-product from the first stage of the Leblanc 
process for the manufacture of soda. The gas is condensed by 
passing up through towers, down through which a stream of water 
falls. (See Manufacture of Alkali.) 

Hydrochloric acid is a monobasic acid. It combines with the 
metals in general to form metallic chlorides, with the liberation of 
hydrogen. With the metallic oxides, it reacts to form metallic 
chlorides and water. A single molecule of HC1 requires but one 
atom of the alkali metals, which have a valency of 1 for its 
saturation, while those metals whose valency is 2, as the alkaline 
earth metals, calcium and magnesium, require two molecules of the 
acid for each atom of the metal. This appears in the following 

reactions : — 

Na 2 + 2 HC1 = 2 NaCl + H 2 0. 

Mg + 2 HC1 = MgCl 2 + H 2 . 

Chlorine and Oxygen. 

Chlorine cannot be made to unite with oxygen directly, but by 
indirect means three different compounds of these two elements 
may be formed : — 

Chlorine dioxide or peroxide C10 2 

Hypochlorous anhydride C1 2 ' 

Chlorous anhydride C1 2 3 

On theoretical grounds there is some reason to believe that the 
two following unknown compounds might exist: — 

Chloric anhydride C1 2 5 

Perchloric anhydride C1 2 7 



HYPOCHLOROUS ACID. 51 

Chlorine dioxide is an unstable, dark-yellow gas, and its prepara- 
tion is attended with danger, on account of the tendency of the gas 
to decompose spontaneously, often with explosive violence. Its 
odor suggests those of chlorine and burned sugar. Euehlorine, 
which has powerful bleaching properties, was at one time con- 
sidered a distinct oxide of chlorine, but is now known to be a mix- 
ture of free chlorine and chlorine dioxide. It is prepared by 
treating potassium chlorate with hydrochloric acid, and is a more 
active decolorizer and disinfectant than chlorine itself. 

The anhydrides of chlorine, as such, possess little practical 
interest ; but, by combination with the elements of water, the cor- 
responding acids, known as the oxy-acids of chlorine, are formed, 
and these are, in some cases, of the highest importance. Thus : — 

G1 2 -f H 2 = 2 HCIO . . Hypochlorous acid, two molecules. 

C1 2 3 + H 2 = 2 HC10 2 . . Chlorous acid, " 

C1 2 5 + H 2 = 2 HCIO3 . . Chloric acid, 

C1 2 7 + H 2 = 2 HC10 4 . . Perchloric acid, " 

Hypochlorous Acid, HCIO. — The first of the oxy-acids of 
chlorine, or that containing the least oxygen, is hypochlorous acid. 
Free HCIO is formed when hypochlorous anhydride, C1 2 (formed 
as a yellow-colored gas by treating mercuric oxide, HgO, with 
chlorine), is passed into water. One volume of water will dissolve 
200 volumes of the gas. Free HCIO is also formed when a dilute 
solution of hydrochloric acid is submitted to electrolysis with 
platinum electrodes. In this case the water and HC1 are simul- 
taneously decomposed by the electricity, the chlorine and oxygen 
appearing at the positive electrode, where they unite with each 
other and combine with water to form HCIO, while hydrogen 
escapes as gas at the negative electrode. Thus : — 

2HC1 + 2 H 2 0, electrolyzed, become 2 HCIO + 2H 2 . 

Hypochlorous acid is a very unstable compound, the oxygen 
atom being apparently very loosely held in the molecule. The 
presence, in a solution of this acid, of almost any oxidizable sub- 
stance is sufficient to determine the reduction of the HCIO mole- 
cule to a molecule of HC1, while the other substance present passes 
to a higher state of oxidation. On this account hypochlorous acid 
is a very powerful bleaching agent, giving up its oxygen with great 



52 GENERAL CHEMISTRY. 

readiness to the coloring-matter of the material to be bleached, 
either forming with it colorless, soluble compounds, or ultimately 
burning it to carbonic acid gas and water. Free hypochlorous acid 
being, however, so difficult of preparation, and of so little stability, 
that it cannot be preserved for any length of time in solution, plays 
no important part in the arts. It unites with the alkali and 
alkaline earth metals to form hypochlorites, which are much more 
stable compounds than the free acid. Common bleaching-powder, 
for example, which consists (at least when dissolved) of calcium 
hypochlorite, CaCl 2 2 , mixed with varying proportions of calcium 
chloride, CaCl 2 , and calcium hydrate, CaH 2 2 , may be preserved 
for a considerable time, with only slow deterioration. (See Bleach- 
ing.) Even in solution, the oxidizing or bleaching action of the 
hypochlorites is much less rapid than that of the free acid, as may 
be shown by the addition of acetic acid, for example, to a solution 
of calcium hypochlorite, and observing the action of portions of the 
solution, before and after the addition of acid, upon two portions 
of unbleached pulp. The acetic acid in this case combines with 
the lime, leaving the hypochlorous acid free. Nor do all the hypo- 
chlorites act as oxidizing or bleaching agents with the same energy 
and rapidity, aluminum hypochlorite being probably the most 
rapid in its action, while sodium hypochlorite is probably the slow- 
est. The magnesium salt acts more rapidly than the calcium salt. 
(Compare Electric Bleaching, Chap. X.) The mode of action of 
the hypochlorites in the process of bleaching is the same as in the 
case of the free acid ; namely, the transference of the oxygen of the 
acid to the organic coloring-material, the hypochlorous acid, in 
both cases, 'being the bleaching agent, or, better, furnishing the 
bleaching oxygen. 

Manufacture of Bleach ing--Powcler. — Chlorine is usually 
prepared for use in the arts by the action of hydrogen chloride, 
HC1 (hydrochloric or muriatic acid), on dioxide of manganese, the 
equation for the reaction being — 

Mn0 2 + 4 HC1 = MnCl 2 (Manganous chloride) + 2 H 2 + Cl 2 . 

By " Weldon's Process," which consists in treating the solution of 
manganous chloride with hot milk of lime or magnesia, and blow- 
ing hot air through the mixture, the manganese may be recon- 
verted into manganese dioxide to be used afresh in the manufac- 
ture of chlorine. " Deacon's Process " for the manufacture of 



BLEA CHING-PO WDEB. 53 

chlorine consists in passing a mixture of gaseous hydrochloric acid 
and air over copper sulphate, heated to about 370° C. By the 
electrolysis of many of the metallic chlorides in a fused state, or 
strong solution, chlorine is obtained at the positive electrode, and 
the metal at the negative (Part II., Chap. X.). 

Bleaching-powder, " chloride of lime," or properly, calcium hypo- 
chlorite, is prepared by passing chlorine over slaked lime, exposed 
in shallow layers to the action of the gas. The absorption 
chambers are usually 60 feet long, 18 feet wide, and 7 feet high. 
They are built sometimes of large flag-stones, but more generally 
of 8-lb. lead, supported by a framework of scantling. The floor is 
made of brick, laid in tar cement over a sheet of lead. Where the 
Deacon process is worked the chambers are divided into sections 
fitted with shelves, upon which the lime is placed ; but in other 
cases the lime is spread upon the floor in a layer from four to five 
inches deep, and is then raked into furrows. 

The chlorine is admitted to the chambers, and is at first rapidly 
absorbed by the lime with evolution of heat. After the lime is 
nearly charged the supply of gas is shut off, so that the chlorine 
remaining in the chambers may be gradually taken up. This 
requires four or five days, and the entire treatment about a week. 

The quality of bleaching-powder depends very much upon that 
of the lime from which it is made, and in order to secure the best 
bleach the lime must be especially pure. A " fat lime," or one 
which slakes easily, is best for the purpose, as it absorbs chlorine 
more quickly and keeps best. Iron and manganese are, of course, 
objectionable in the lime, on account of the color which they im- 
part to the bleaching-powder, and they are also said to impair the 
keeping qualities of bleach in which they occur. 

Clay and silica injure the quality of bleach, since they cause it 
to settle slowly and imperfectly ; while bleach containing magnesia 
has an increased tendency to take up water and become pasty 
through the formation, according to Lunge, of magnesium chloride. 

In order to prepare bleaching-powder it is necessary that the 
lime contain some water. Partially slaked lime may be imperfectly 
chlorinated, but the best results are obtained when dry chlorine is 
used and the slaked lime contains 2 to 4 per cent, excess of water. 
The temperature at which absorption takes place has a decided 
influence upon the strength and quality of the product, through 
the formation of chlorate at the higher temperatures. The best 



54 GENERAL CHEMISTRY. 

authorities prefer a temperature not above 40° to 55° C. Hurter 
gives as the maximum 40° ; Bobierre, 50° ; Sheurer-Kestner, 55°. 
The experiments of Schappi, who used moist chlorine, gave at — 

Temperature Available chlorine Temperature Available chlorine 

° C. per cent. ° C. per cent. 

-17 2.30 40 41.18 

19.88 45 40.50 

7 33.24 50 41.52 

21 35.50 60 39.40 

21 (25?) . . 39.50 90 4.26 

. 30 40.10 

Good bleach should be a pure white powder, containing some 
lumps if the test is high, and having a faint odor of hypochlorous 
acid. It should become tough when kneaded with the fingers. 
The lumps should not contain a core of lime, but should be con- 
verted to bleach throughout, and should break down easily between 
the fingers. The formula usually given for bleaching-powder is 
CaCl 2 2 , but the latest experiments of Lunge point to the formula 
CaOCl 2 . There is usually present also a little calcium chlorate, 
chloride, and free lime. 

Chlorous Acid, H00 2 . — This acid, containing one more atom 
of oxygen in its molecule, is formed by the action of nitric acid 
on potassium chlorate. It is never met with ordinarily in the 
free state, as it is a dangerous compound. In combination with 
bases, however, as chlorites, it is of not infrequent occurrence. 
Chlorites are formed by the electrolysis of solutions of the alkali 
and alkaline earth chlorides, under regulated conditions. They 
are bleaching agents of less energy than the hypochlorites, and are 
of little importance. 

Chloric Acid, HC10 3 . — This acid is of no importance in the free 
state. Its chief salt of commerce is potassium chlorate, KC10 3 . A 
solution of this salt does not bleach in the cold, but on heating, 
with the addition of a mineral acid, it oxidizes organic matter with 
great energy. The dry salt forms powerful explosive mixtures 
with sulphur, phosphorus, many of the minerals, and organic 
matter generally. A mixture of sugar and chlorate of potassium, 
powdered separately, and cautiously mixed to avoid friction, will 
be set on fire by a drop of strong sulphuric acid. Potassium 
chlorate is formed by passing a stream of chlorine gas through a 
warm solution of caustic potash. Chlorates are also formed by the 



BROMINE. 55 



electrolysis of solutions of the chlorides, under certain conditions 
of strength of solution and current, and especially of tempera- 
ture of solution, elevation of temperature favoring their forma- 
tion at the expense of that of the hypochlorites. Chlorate of lime 
occurs in small and varying percentage in bleaching-powder. 

Perchloric Acid, H00 4 . — This is a colorless, volatile liquid, 
and is a very powerful oxidizing agent. It forms perchlorates. 
Neither the acid nor its salts are of any importance except as 
chemical reagents. 

Chlorine and Nitrogen. 

Chlorine combines with nitrogen to form a single compound, 
which we mention here simply on account of its extremely danger- 
ous character. It is an oily liquid, heavier than water. It explodes 
spontaneously, and with extreme violence, below 100° C. Its 
formula is probably NC1 3 . It is formed by the action of chlorine 
gas on a strong solution of chloride of ammonia, sal ammoniac, and 
also when such a solution of sal ammoniac is electrolyzed. 

Chlorine and Sulphur. 

Chlorine combines directly with sulphur, forming — 

Sulphur chloride S 2 C1 2 

Sulphur dichloride SC1 2 

Sulphur tetra-chloride . . . . . . . . SC1 4 

These compounds are all liquids of some value to the chemist, but 
having few practical applications. 

BROMINE. 

Symbol, Br. — Atomic weight, 80. — Molecule, Br., . — Molecular weight, 160. 

Bromine is a deep-red liquid of specific gravity 2.976. It freezes 
at — 2-H C, and boils at 63° C. It volatilizes rapidly at ordinary 
temperatures in red fumes of a very disagreeable odor, and ex- 
tremely irritating to the mucous membrane of the throat and eyes. 
Bromine is little soluble in water, more readily in alcohol and 
ether. Bromine was discovered by Balard in 1826. It is contained 
in combination with alkaline bases, in sea-water, and in the water 
of many mineral springs. It never occurs native. 



56 GENERAL CHEMISTRY 



Bromine resembles chlorine very markedly in all its properties, 
forming throughout analogous compounds. In chemical activity, 
however, it is somewhat less energetic. It finds many uses in the 
arts and in medicine ; but, aside from its close relation to chlorine, 
is of little interest to the paper-maker. 



IODINE. 

Symbol, I. — Atomic weight, 127. — Molecule, I 2 . — Molecular weight, 254. 

Iodine bears great resemblance in its chemical properties to 
chlorine and bromine, but differs from both in being, at ordinary 
temperatures, a solid crystalline substance, of a steel-blue color 
and metallic lustre. It has a specific gravity of 4.95. Iodine 
melts at 107° C, and boils at 175° C, the vapor having a deep 
violet color. It volatilizes quite rapidly at ordinary temperatures. 
Iodine is very slightly soluble in water, but easily in alcohol and 
in a solution of potassium iodide. 

It was discovered by Courtois in 1811, in the ash of sea-weeds. 
It occurs usually as sodium iodide in sea-water and in many 
mineral springs. Iodine never occurs native. It is of great value 
both free and in combination in medicine, and finds many uses in 
the arts. 

Its compounds are all analogous to those of chlorine and bromine. 
A solution of iodine in potassium iodide is of great value in the 
sulphite pulp process, since it furnishes a ready means of deter- 
mining the total amount of sulphurous acid in the bisulphite solu- 
tion used. (Compare Analysis of Bisulphite Liquors.) 



FLUORINE. 

Symbol, F. — Atomic weight, 19. — Molecule, F 2 . — Molecular weight, 38. 

Fluorine is an extremely energetic and corrosive gaseous ele- 
ment, never found native. It forms, with hydrogen, hydrofluoric 
acid, HF, corresponding to hydrochloric acid, and is interesting 
from its property of dissolving or etching glass ; hence it must be 
preserved in leaden or gutta-percha bottles. Hydrofluoric acid 
is a dangerous substance to handle, owing to its injurious action 
on the throat and lungs. The chief natural compounds of fluorine 
are calcium fluoride, or fluorspar, CaF 2 , and sodium-aluminum 



BORON. 57 

fluoride, or cryolite, 3 NaF, A1F 3 . The latter is the raw material 
from which " Natrona " alum and "Natrona " bicarbonate of soda 
are made. It is obtained from Greenland. 

These four elements — chlorine, bromine, iodine, and fluorine — 
are often classed together as the chlorine group, from their similar- 
ity in their chemical characters, and in the formation and nature 
of their compounds. 

They are also sometimes denominated the halogens, and their 
compounds the halogen compounds. It is interesting to note in 
this connection how the chemical activity of the members of the 
group falls as the atomic weight rises. 

BORON. 

Symbol, B. — Atomic weight, 11. — Molecule, B., . — Molecular weight, 22. 

Boron is a solid element, never native, and of no interest except 
in combination. It has a valency of three, one atom being the 
equivalent of three atoms of hydrogen in combining power. Thus 
it forms with chlorine, BC1 3 , boron chloride, and with fluorine, 
BF 3 , boron fluoride. The latter is interesting as being one of the 
few reagents which give a direct qualitative reaction with cellulose, 
which is blackened by boron fluoride. 

Boron always occurs in nature combined with oxygen as boracic 
acid (or boric acid), H 3 B0 3 , either free or in combination. Boracic 
acid is soluble in three parts of boiling water, from which it crys- 
tallizes on cooling in pearly, mica-like scales, requiring 25 parts 
of water at 18° C. for solution. Boracic acid is soluble in alcohol, 
and when alcohol containing it in solution is burned the acid im- 
parts a green color to the flame. 

The chief salt of boracic acid is borax, sodium biborate, 
Na 2 B 4 T , 10 H 2 0, which is found native in large quantities in Cali- 
fornia and certain other places. Borax is of considerable use in 
the working of iron and many other metals, from its property of 
dissolving or forming a flux with many metallic oxides when fused 
with them. Borax possesses marked detergent qualities, owing 
largely to the power of its solutions of dissolving and partly 
saponifying fatty matters. It also, when in solution, forms a ready 
solvent for shellac, one part of borax being sufficient to render 
soluble about five parts of shellac. Alum and lime salts reprecip- 
itate the p'um. 



58 GENERAL CHEMISTRY. 

Solutions of boracic acid and its salts possess quite marked 
antiseptic properties, and on that account are of considerable im- 
portance. They also possess medicinal properties. 



SILICON. 

Symbol, Si. — Atomic weight, 28. 

Silicon never occurs native, but combined with oxygen as silicic 
anhydride, Si0 2 , or silica, it is one of the most abundant of 
minerals. The elementary substance was first isolated by Berzelius 
in 1823. It may be prepared with some difficulty in two forms, — 
amorphous silicon, a brown powder heavier than water, and a non- 
conductor of electricity ; and crystalline silicon, a steel-gray sub- 
metallic crystalline substance of specific gravity 2.49, and which is 
a conductor of electricity. By electrolysis of certain compounds of 
silica, in a state of fusion with metallic compounds, alloys of silicon 
may be obtained. They, however, present more of the characters 
of a solution, if we may so term it, of the silicon in the metal than 
of true homogeneous alloys. Rock crystal, or quartz, is pure silica, 
Si0 2 . Amethyst, agate, flint, carnelian, onyx, etc., are nearly pure 
silica, colored by small quantities of metallic oxides. By fusion 
with carbonate of soda, silicate of soda is formed, which is a sub- 
stance having the appearance of glass, but soluble in water, hence 
called soluble glass. Ordinary glass is a more or less pure silicate 
of lime, containing some soda and some metallic oxides, as man- 
ganese, lead, and iron oxides. 

Ordinary clay is a mixed silicate of alumina, lime, magnesia, etc., 
usually containing other metallic silicates, which give it color. 
Kaolin, or china clay, is very nearly pure silicate of aluminum, 
the impurities being varying amounts of silicates of lime and mag- 
nesia. It contains no iron or other colored metallic oxides. 

The value of a clay for a paper-maker's use is largely dependent 
on the proportion of silicate of alumina it contains, and its freedom 
from iron oxide, sand, and grit. 

Silicon forms compounds with chlorine, bromine, iodine, and 
fluorine, SiCl 4 , SiBr 4 , Sil 4 , and SiF 4 . They are solely of interest 
and use to the chemist. 



PHOSPHORUS. 59 



PHOSPHORUS. 

Symbol, P. — Atomic weight, 31. — Molecule, P 4 . — Molecular weight, 124. 

Phosphorus is a translucent, slightly yellow substance of specific 
gravity, 1.83, and resembling wax in appearance. It possesses a 
peculiar odor suggestive of garlic. It melts at 44° C, and boils 
at 290° C. It is insoluble in water ; somewhat soluble in ether, 
turpentine, and oils. It is freely soluble in carbon disulphide. 

Phosphorus was discovered by Brandt in 1669. It takes its 
name from two Greek words meaning " light-bearer," and was so 
called on account of its property of emitting light when exposed to 
the air. 

It is never found native, but in combination with lime is widely 
distributed in nature. It forms an essential element in the com- 
position of the bones, blood, brain, and other portions of the 
animal economy, and is always necessary to the development of 
seed in plants. 

Although in combination with oxygen it is so essential to animal 
life, yet in the free state it forms a virulent poison, excepting in 
a single one of its amorphous forms. This latter modification, 
known from its color as red phosphorus, is prepared by heating 
ordinary phosphorus in an atmosphere of carbonic anhydride for 
thirty or forty hours, at a temperature of 230° to 240° C. It then 
forms a red powder, insoluble in all media. It is non-poisonous, 
and does not, like ordinary phosphorus, need to be preserved under 
water, as the red variety does not inflame below 260° C. Phos- 
phorus is prepared from calcium phosphate, by distillation with 
charcoal, the vapors of phosphorus produced being condensed and 
the resulting phosphorus preserved under water. On account of 
its inflammability phosphorus is a very dangerous substance, and 
must be kept under water and handled with extreme care. 

Phosphorus forms a great variety of compounds of extended use 
in medicine and in the arts, but none have any immediate bearing 
on the art of paper-making, and on that account may be omitted 
here. 

Phosphorus combines directly with metals, when heated with 
them, to form phosphides of the metals, and in many cases the 
phosphides may be alloyed directly with other metals. When 
present in veiy small quantities the phosphides serve to impart to 
metals characters quite distinct from those of the pure metals. 



60 GENERAL CHEMISTRY. 

In most cases the presence of phosphorus in a metal is objec- 
tionable, while in a few instances, as, for example, in "phosphor 
bronze," it imparts very useful properties to the metal or alloy. 
Phosphor bronze is an alloy of copper and tin, and contains a 
small amount of phosphide of tin, which gives the alloy marked 
acid-resisting quality, besides increasing its strength and tough- 
ness. 

ARSENIC. 

Symbol, As. — Atomic weight, 75. — Molecule, As 4 . — Molecular weight, 300. 

Arsenic is sometimes found native, but more commonly occurs 
in combination with metals and sulphur as sulpho-arsenides. Ar- 
senicum, as it is frequently written, occupies the border line be- 
tween the non-metallic substances and the metals. In its phys- 
ical characters, and in its combinations with sulphur, it approaches 
more nearly the metals ; while in the formation of anhydrides, 
Aso0 3 and As 2 5 , and their corresponding acids, H 3 As0 3 and 
H 3 As0 4 , as well as in most of its other chemical characters, it 
plays the part of a non-metal. Pure arsenic is a steel-gray sub- 
stance, having a bright, metallic lustre. It tarnishes rapidly in the 
air. Its specific gravity is about 5.8. Heated in the air, it burns 
Avith a bluish flame. Nearly all the compounds of arsenic are 
extremely poisonous. The common arsenic of the shops, or white 
arsenic, is arsenious anhydride, As 2 3 . Paris green is aceto- 
arsenite of copper. 

The common rat-poisons and potato-bug poisons are nearly all 
preparations of arsenic. Some of the compounds of arsenic are of 
great use in the arts. In the manufacture of aniline colors many of 
the most brilliant and beautiful shades are best obtained by the use 
of compounds of arsenic. In these colors it is the aim of the manu- 
facturer to remove the arsenic in a subsequent process of the 
manufacture. Unfortunately the removal is often incomplete, and 
numerous cases of arsenical poisoning, more or less acute, have 
occurred from the presence of arsenic in the colors of wall-paper or 
in the dye of carpets or clothing. The presence in wall-paper of 
the equivalent of a quarter of a grain of white arsenic per square 
yard is considered dangerous. 

Arsenious acid in solution, either in hydrochloric acid or dis- 
solved in water as arsenite of soda, is readily oxidized by chlorine, 



ARSENIC. 61 

or a hypochlorite, into arsenic acid, and so furnishes the analyst 
with a ready means of determining the " available chlorine " in a 
solution of bleaching-powder. (Compare Analysis of Bieaching- 
powder.) 

The preceding fifteen elements comprise all the non-metallic 
elements at present known. The oxides of all these elements are 
called anhydrides, and unite with water to form acids, either mono- 
basic, di-, tri-, or tetra- basic, according as they contain respectively 
one, two, three, or four atoms of hydrogen, which may be replaced 
by a metal. 



62 GENERAL CHEMISTRY 



THE METALLIC ELEMENTS. 

There are at least forty-nine known metals. Many of them 
are, however, of small importance, and indeed have been but little 
investigated. 

All the metals combine with oxygen to form oxides, which in 
turn may unite directly with anhydrides (oxides of the non-metals) 
to form salts. The oxides of the non-metals (anhydrides) unite 
with water to form acids, while the metallic oxides unite with 
water to form hydroxides, sometimes called hydrates or bases. 
Acids and hydroxides unite to form metallic salts, with the elimina- 
tion of water ; thus, hydrochloric acid, HC1, and sodium hydroxide, 
NaHO, unite to form sodium chloride, NaCl, and water, H 2 — 



HC1 + NaHO = NaCl + H 2 0. 



A few of the metals form both acid and basic oxides, standing 
as it were on the dividing line between the non-metals and the 
metals. 

A very large proportion of the oxides are insoluble in water, and 
also most of the metallic salts, with the exception of the chlorides, 
nitrates and sulphates, which are nearly all soluble in water. 

The metals are all good, though not equally good, conductors of 
heat and electricity. They are all opaque substances, capable in 
the mass of receiving a more or less polished surface, and they 
exhibit a peculiar lustre, termed metallic. They show various 
degrees of hardness, from the consistency of putty to the hardness 
of steel. The brittleness of metals is much increased by lowering 
of temperature. All exhibit a considerable degree of tenacity, or 
resistance to a breaking strain. Many of the metals are malleable ; 
that is, may be extended under rollers or beaten into sheets. In 
the latter regard gold takes the first rank. Gold leaf may be made 
only -2 swoo °f an incn m thickness. 

The specific gravity of the metals varies greatly, lithium being 
the lightest, specific gravity 0.59, and osmium the heaviest, specific 
gravity 22.48. 



POTASSIUM. 63 



Many of the metals occur in nature in the form of crystals. The 
metals combine together under the influence of heat to form alloys, 
the melting-point of the alloy often being below that of any of the 
constituent metals. The alloys appear, in some respects, to be true 
chemical compounds, but are not in general so regarded. Alloys 
of mercury are called Amalgams. 



THE ALKALI METALS. 

The alkali metals are six in number: — 



Potassium : 


Symbol, 


K. 


— Atomic 


weight, 39.1 


Sodium : 


Symbol, 


Na. 


— " 




" 23. 


Lithium : 


Symbol, 


Li. 


— " 




" 7. 


Caesium : 


Symbol, 


Cs. 


— " 




" 133. 


Rubidium : 


Symbol, 


Rb. 


u 




" 85.4 


[Ammonium] 


: Symbol, 


NIL, 


— Combining 


" 18. 



The alkali metals all have a valency of 1 ; that is, are capable of 
replacing the hydrogen of an acid atom for atom. Their hydrox- 
ides are very soluble in water, and their solutions are strongly 
alkaline to test paper, and caustic and destructive in their action 
upon animal substances. Their carbonates are soluble in water, 
and these solutions are also alkaline. 

POTASSIUM. 

Symbol, K. — Atomic weight, 39.1. — Specific gravity, 0.865. 

Potassium is a brilliant, bluish-white metal, which melts at 
62l° C, and volatilizes at a red heat in green vapors. It is never 
found native, but its compounds are widely distributed, being 
found in mica, feldspar, all fertile soils, sea-water, and in large 
quantities in the salt deposits at Stassfurt, Germany. ■ The metal 
oxidizes so rapidly that it has to be preserved under naphtha or 
some other liquid which contains no oxygen. When thrown upon 
water it decomposes the latter, uniting with the oxygen, and dis- 
solving as hydroxide, KHO, and setting free the other atom of 
hydrogen. So much heat is developed in the reaction that the 
hydrogen takes fire, its flame being colored violet by the vapor of 
potassium. This violet-colored flame furnishes a ready test for the 
metal. 

Potassium oxide, K 2 0, is the potash of chemists. It is formed 
by the dry oxidation of potassium. It unites with water molecule 



64 GENEBAL CHEMISTRY, 



for molecule (K 2 + H 2 = 2 KHO) to form potassium hydroxide, 
or hydrate, KHO, commercially called caustic potash. This is a 
hard, grayish-white solid, which dissolves very readily in water, 
with development of much heat. It attracts moisture from the 
air so rapidly as to become liquid in a short time. This action is 
called deliquescence. Potassium hydrate is a very caustic and 
powerful base. It precipitates the metals as hydrates from nearly 
all solutions of metallic salts. It forms compounds with all the 
acids, many of these compounds being of great importance. With 
fats and oils it forms hard soaps, Avhile soda forms soft soaps. 

Potassium carbonate, K 2 C0 3 , is very similar to soda-ash, which 
is sodium carbonate. The crude potassium salt is obtained from 
wood ashes by leaching them and evaporating the solution, and 
is called crude potashes. It is mainly used in the manufacture of 
glass and soap. 

Potassium nitrate, KN0 3 , is saltpetre, an important ingredient in 
gunpowder, of which it forms about three-fourths the weight. Its 
use here and in fireworks is due to the readiness with which it gives 
up its oxygen. 

Potassium chlorate, KC10 3 , is, like saltpetre, a white, crystalline 
salt, largely used in fireworks and matches to supply oxygen. It 
is also used in medicine. 

Potassium chloride, KC1, much resembles common salt; the 
bromide, KBr, is a valuable medicine. The ferrocyanide, yellow 
prussiate of potash, forms with iron (ferric) salts the well-known 
Prussian blue. 

Potassium tartrate is " cream of tartar." 

SODIUM. 

Symbol, Na. — Atomic weight, 23. — Specific gravity, 0.972. 

Sodium is a beautiful crystalline metal, of silver-white appear- 
ance. It fuses at 97.6° C, volatilizes at a red heat, and greatly 
resembles potassium in all its properties. Sodium never occurs 
native, but in combination it is of universal occurrence. Potassium 
and sodium correspond very closely in all their chemical combina- 
tions, the chemical activity of the latter being, however, somewhat 
weaker than that of the former. 

Sodium hydroxide, or caustic soda, NaOH, is a white, fusible, 
deliquescent solid, very soluble in water, though less so than 
caustic potash. It is a powerful alkali. 



S0DIU3L 65 

The most commonly occurring salt of sodium is the chloride, 
NaCl, or " common salt." It is obtained by the evaporation of sea- 
water, the water of salt springs and wells, and is also mined as 
rock salt. Common salt crystallizes generally in cubes. It is solu- 
ble in 2i times its weight of water at 15i° C. It fuses and volatil- 
izes at a red heat. Hydrochloric acid is made by distilling sodium 
chloride with sulphuric acid, 2 NaCl + H 2 S0 4 = Na 2 S0 4 + 2 HC1. 
Glauber's salt is crystallized sodium sulphate, Na 2 S0 4 , 10 H 2 0. 
Soda-ash is more or less pure anhydrous, or dry, sodium carbonate, 
Na 2 C0 3 . "Soda crystals," or "washing-soda," is crystallized 
sodium carbonate, Na 2 C0 3 , 10 H 2 0. Common baking-soda is sodium 
bicarbonate, NaHC0 3 . (For description of processes of manufac- 
turing soda-ash, etc., see Manufacture of Alkali.) Borax is sodium 
biborate, Na 2 B 4 7 , 10 H 2 0. Borax is found native in California. It 
is soluble in 12 parts of cold, and in one-half part, or one-half its 
weight of boiling water. Borax when heated swells up, loses its 
water of crystallization, and finally, at about a red heat, melts to 
a clear glass. It is of great value as a flux in metal working. 

Sodium nitrate, NaN0 3 , is found native in Peru and Chili, and 
is imported from these places in large quantities. It has very 
nearly the same properties as saltpetre, KN0 3 , but cannot be sub- 
stituted for the latter in gunpowder, since it attracts moisture. 
Saltpetre is made from sodium nitrate by what is called double 
decomposition between that salt and potassium chloride. When 
solutions of the two salts are mixed in the proper proportions an 
interchange of acids and bases occurs, and potassium nitrate and 
sodium chloride result — 

NaN0 3 + KC1 = KNO» + NaCl. 

The normal salts of sodium are all soluble in water, with the single 
exception of pyr-antimonate of sodium, Na 2 Sb 2 7 , 6 H 2 0. 

The compounds of sodium are the most useful in the variety and 
extent of their applications of any of the salts of the alkalis. 

Manufacture of Alkali. — The manufacture of soda-ash from 
common salt, by the Leblanc process, depends primarily upon the 
following reactions : — 

Common salt. Sulphuric acid. Acid sodium sulphate. Hydrochloric acid. 

(1) NaCl + H 2 S0 4 = NaHS0 4 -f HC1. 

Sodium sulphate. 

(2) NaCl + NaHS0 4 = Na 2 S0 4 + HC1. 



66 • GENERAL CHEMISTRY. 

(3) By heating sodium sulphate, Na 2 S0 4 , with carbou in the form 
of coal and with chalk, calcium carbonate, CaC0 3 , the various reactions 
shown below are set up, which result in the production of black-ash, 
from which sodium carbonate may be extracted by lixiviation. These 
phases of reaction (3) may be regarded thus — 

Carbon. Sodium sulphide. Carbon monoxide. 

(a) 5Na 2 SO 4 + 10C = 5Na 2 S + 10 CO. 

Calcium sulphide. 

(6) 5Na 2 S + 5CaC0 3 =.5Na 2 CO a + 5 CaS. 

Caustic lime. 

(c) 2CaC0 3 + 2C = 2 CaO + 4 CO. 

Reactions (1) and (2) on page 65 are carried out in iron pots, 
set in a furnace, and. containing the charge of salt, upon which 
the sulphuric acid is run. The torrents of hydrochloric acid gas 
which are evolved pass out of the furnace and up through scrub- 
bers, or towers, filled with flints, down which a stream of water 
trickles. The gas is absorbed by the water, forming commercial 
muriatic acid, which flows from the bottom of the tower. The 
sodium sulphate, or salt cake as it is technically termed, is removed 
from the pots and made up into what is called black-ball, with 
coal, lime, and limestone or chalk. This mixture is furnaced, and 
under the influence of heat the various phases of reaction (3) 
are set up, and black-ash, yielding in different works from 23 
to 45 per cent, of sodium carbonate, with a much smaller and 
varying percentage of caustic soda, is obtained. The carbonate 
and caustic are removed by washing the black-ash with water, 
and the solution is either subjected to minor operations to purify 
the subsequent product, or is run down at once to obtain the 
commercial soda-ash. For the preparation of caustic soda the 
black-ash liquors are usually treated at once with lime, air is 
blown through the mixture to decompose sulphides, etc., and the 
caustic liquor decanted and evaporated. In many works the 
caustic is produced at once in the furnace by somewhat increasing 
the quantity of coal added to the mixture of salt cake and lime- 
stone, and lixiviating the ball-soda at once with water at 50°. 

The hydrochloric or muriatic acid obtained in reactions (1) and 
(2) above is decomposed as described under Chlorine, for the 
manufacture of bleaching-powder, or more rarely of potassium 
chlorate. 



SODIUM. 



67 



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68 GENERAL CHEMISTRY. 

A large and increasing quantity of high-grade soda-ash is now 
manufactured by the Solvay or ammoniacal process, which depends 
upon the fact that if common salt is dissolved in ammonia water, 
and a current of carbonic acid gas passed through the solution, 
ammonium chloride is formed and sodium bicarbonate precipitated. 
The bicarbonate is then washed free from the solution, and upon 
ignition yields the carbonate. The ammonia is recovered by heat- 
ing the ammonium chloride with lime, the chlorine combining with 
the lime to form calcium chloride, which is a waste product. On 
account of this loss of chlorine no bleaching-powder is made by 
this process. 

LITHIUM. 

Symbol, Li. — Atomic weight, 7. — Specific gravity, 0.59. 

Lithium is a white, lustrous metal, discovered by Arfwedson in 
1818. It is the lightest solid known, being only about one-half as 
heavy as water. It is fusible at 180° C, and volatile at a red heat. 
It occurs as chloride in many mineral springs, and as silicate or 
fluoride in not a few minerals. It is of no importance other than 
as a medicinal agent. 

CiESIUM. 

Symbol, Cs. — Atomic weight, 133. 

RUBIDIUM. 

Symbol, Kb. — Atomic weight, 85.4. 

Both these metals were discovered by Bunsen and Kirchoff in 
spring waters in Hungary. They are present also in a few minerals. 
Traces of csesium have also been found in the ashes of tobacco, 
beetroot, coffee, and grapes. Both are very rare metals, and form 
no compounds of any commercial importance. 

AMMONIUM. 

Symbol, NH 4 . — Combining weight, 18. 

Ammonium (a compound of hj^drogen and nitrogen, not to be 
confounded, however, with ammonia, NH 3 ) is not in reality a 
metal, but in many of its combinations so nearly plays the part of an 
alkali metal, and its compounds are so similar to the corresponding 



METALS OF THE ALKALINE EARTHS. 69 

compounds of potassium and sodium, that they may be best con- 
sidered here. 

Ammonium unites with water to form ammonium hydrate or 
hydroxide, NH 4 OH, the common ammonia water, which possesses 
all the alkaline properties, though in less degree, of a solution of 
potassium or sodium hydrate. 

It unites with acids to form ammonium sulphate (NH 4 ) 2 S0 4 , 
chloride (NH 4 )C1, carbonate (NH 4 )C0 3 , etc., strictly analogous to 
the corresponding salts of the alkali metals. 

Ammonium is often carelessly mistaken for hydrogen nitride, or 
ammonia, NH 3 , but it should never be, as it is entirely distinct. 
Ammonia, NH 3 , never enters into combination with acids to form 
salts, these compounds always being formed from ammonium, 
NH 4 . Ammonia by contact with water is changed into ammonium 
hydroxide (NH 4 )OH, which then may perform all the functions of 
any other alkaline hydroxide. 

Ammonium, NH 4 , is a good type of what is called a Radicle; that 
is, an unsaturated group of atoms, which in combination plays the 
part of a single atom. The number of such groups or radicles 
known to organic chemistry is very large, and in many cases, by 
the coalescence of two groups of the same kind, a stable molecule 
is formed, so that the radicle can exist in the free state. Cyanogen, 
— C = N, is such an organic radicle, the molecule of free cyanogen 
being N = C - C = N. 



METALS OF THE ALKALINE EARTHS. 

Barium: Symbol, Ba. — Atomic weight, 137. — Specific gravity, 4.000. 
Strontium: Symbol, Sr. — " " 87.5.— " " 2.540. 

Calcium: Symbol, Ca.— " " 40. — " " 1.578. 

These metals all decompose water at the ordinary temperature. 
They form oxides of an earthy nature. These combine with water 
(slake), forming hydroxides, which dissolve somewhat in water, 
forming alkaline solutions. All are strong bases. Their carbon- 
ates are insoluble. Their bicarbonates and most of their other 
salts are soluble in water. One atom of each can replace two 
atoms of acid hydrogen. 



70 GENERAL CHEMISTRY. 

BARIUM. 

Symbol, Ba. — Atomic weight, 137. — Specific gravity, 4.000. 

Barium is a silver-white metal, which melts below a red heat 
and oxidizes readily. It may be obtained by the electrolysis of 
fused barium chloride. 

Barium oxide or caustic baryta is obtained by calcining barium 
carbonate, BaC0 3 , at a red heat. It combines eagerly with water, 
with the development of much heat, and forms barium hydroxide 
or hydrate, BaH 2 2 . The hydroxide is soluble in 20 parts of cold 
or two parts of boiling water. 

The solution is strongly alkaline. Barium hydrate and all the 
soluble salts of barium are very poisonous, their antidotes being 
sodium or magnesium sulphate. 

The soluble salts of barium are the chloride, BaCl 2 , 2 H 2 0, nitrate, 
BaN 2 6 , chlorate, BaCl 2 6 , the acetate, BaC 4 H 6 4 , 8 H 2 0, and the 
thiosulphate, BaS 2 3 ,H 2 0. Barium sulphate, BaS0 4 , is insoluble. 
It is frequently employed as an adulterant of white lead in paint, 
and to some extent as a filler in paper. It is found native as 
" Heavy spar." Barium carbonate is also found native as " With- 
erite." The soluble salts of barium impart a green color to the 
colorless flame of alcohol or of the Bunsen gas-burner. 

Barium oxide, when heated in a current of dry air, takes on a 
second atom of oxygen, the peroxide, Ba0 2 , being formed. At a 
still higher temperature the peroxide is reduced to the original 
barium oxide, BaO, oxygen being at the same time liberated. This 
reaction has been made use of in the preparation of ox} r gen on the 
large scale, the barium oxide being alternately brought to the 
lower and higher temperature in retorts, which are first connected 
with a source of air, and then with gas-holders. The Brins, who 
have developed the process in the commercial way, prepare a solu- 
tion for bleaching paper stock by saturating hydrochloric acid with 
oxygen. 

Barium peroxide is also interesting as furnishing a means for 
preparing hydrogen peroxide, H 2 2 . Thus, when barium peroxide 
is treated with water and hydrochloric acid, barium chloride and 
hydrogen peroxide are formed — 

BaO, + 2 HC1 = BaCl 2 + H 2 0„, 

both products remaining in solution. 



CALCIUM. 71 



When sulphuric acid is employed barium sulphate is precipi- 
tated, and a pure solution of hydrogen peroxide in water is obtained, 
which may be used for bleaching or other purposes. 

STRONTIUM. 

Symbol, Sr. — Atomic weight, 87.5. — Specific gravity, 2.54. 

Strontium is a yellow metal, somewhat harder than lead. In its 
properties and reactions it is very similar to barium. Its hydrox- 
ide, SrH 2 2 , is somewhat less soluble than barium hydroxide, while 
most of its compounds are more soluble than the corresponding 
barium compounds. Strontium compounds impart a crimson color 
to flame. They find their chief employment in the manufacture 
of "red fire." The hydroxide forms a comparatively insoluble 
compound with sugar (sucrose), and hence affords a means of 
separating the latter from the uncrystallizable sugar of molasses. 

CALCIUM. 

Symbol, Ca. — Atomic weight, 40. — Specific gravity, 1.578. 

Calcium is never found native, but its compounds, especially the 
carbonate, silicate, and phosphate, are widely distributed, and are 
of great use and value. The metal calcium is prepared with con- 
siderable difficulty, and is of no importance as a metal. It is of a 
light-yellow color, about as hard as gold ; is malleable and ductile. 
It tarnishes slowly in dry air, and decomposes Avater rapidly at the 
ordinary temperature. When heated in oxygen it burns with a 
magnificent rose-red flame. Like barium, it forms two oxides, CaO 
and Ca0 2 , the former only being of importance. Calcium oxide, 
CaO, is ordinary " quicklime." It is a white, caustic, earthy sub- 
stance, infusible when pure. When heated in the oxyhydrogen 
flame it glows with an intense white light, rivalling the light of 
the electric arc. Calcium oxide combines with water with the 
development of great heat, and " slakes " into calcium hydroxide 
or hydrate, CaH 2 2 . The latter substance is a strongly alkaline 
base, soluble in 700 times its weight of cold water, but much less 
soluble in boiling water. 

A clear saturated solution of calcium hydrate is the lime-water 
of pharmacy, and water containing more CaH 2 0, than it is able to 
dissolve is called milk of lime. Calcium hydroxide forms the basis 



GENERAL CHEMIS TB Y. 



of mortars and cements. The hardening or setting of mortar is 
brought about by the combination of the lime with the carbonic 
acid of the atmosphere to form carbonate of lime, aided by the 
silica of the sand used, which forms silicate of lime to a small 
extent. 

" Hydraulic lime " is lime which contains free soluble silica. 
Such lime, when moistened, first slakes and then in a short time 
sets to a hard mass through the combination of the lime with the 
soluble silica, forming stone. 

This setting will take place even under water. Hydraulic lime 
is employed in the manufacture of Portland cement, and gives the 
cement its valuable properties. Calcium hydrate is capable of 
many useful applications, as in causticizing soda (compare Soda- 
ash), preparing indigo for coloring, as a "base" in the sulphite 
pulp process, and in the manufacture of bleaching-powder, etc. 

Calcium oxide, CaO, is prepared by calcining, or burning, lime- 
stone, calcium carbonate, CaC0 3 , in a kiln. The heat decomposes 
the calcium carbonate, driving off the carbonic acid as gas, C0 2 , 
while the stone is changed into quicklime, CaO. Marble and 
chalk are nearly pure calcium carbonate, while ordinary limestone 
contains varying amounts of magnesia, iron oxide, alumina, silica, 
etc. A lime for building purposes may contain quite considerable 
amounts of impurities other than magnesia without seriously injur- 
ing it. On the other hand, a lime for sulphite liquor making may 
contain almost any amount of magnesia, though moderate amounts 
of other impurities are objectionable ; while lime intended for the 
manufacture of bleaching-powder must be very nearly pure CaO. 

Calcium hydrate is a strong base. Some of the salts of calcium 
are extremely soluble in water, as the chloride, CaCl 2 , nitrate, 
CaN 2 6 , and the chlorate, CaCL0 6 . A larger number are moder- 
ately soluble, as the hypochlorite, CaCL0 2 , sulphate, CaS0 4 , etc.; 
while not a few are almost absolutely insoluble, as the carbonate, 
CaC0 3 , the sulphite, CaS0 3 , and the phosphate, Ca 3 P 2 8 . In some 
cases the insoluble salts of calcium may combine with a second 
equivalent of the acid, as the carbonate, to form bicarbonate, and 
the sulphite to form bisulphite, the latter salts being largely solu- 
ble. The so-called " hard " waters often contain calcium bicarbon- 
ate. In this case boiling removes the " hard " quality, the second 
equivalent of carbonic acid being liberated by the heat, and the 
lime precipitated as the insoluble carbonate. Bisulphite of lime 



MAGNESIUM. 73 

solutions are decomposed in a similar way by boiling, with the pre- 
cipitation of calcium sulphite. Other soluble salts of lime produce 
"hardness" in water, which remains after boiling, and hence is 
called "permanent hardness." 

Selenite, gypsum, anhydrite, and alabaster are all different nat- 
ural forms of calcium sulphate, CaS0 4 . "Pearl hardening," "pearl 
pulp," and " crown filler " are artificial sulphate of lime, prepared 
for use as "fillers" in paper. Crystallized sulphate of lime, CaS0 4 , 
2 H 2 0, is soluble in 400 times its weight of water, or one pound in 
about 48 gallons, at the ordinary temperature. It is less soluble in 
hot water. At 100° G. sulphate of lime loses three-fourths of its 
water of crystallization ; at about 260° C. still more is lost, and it 
becomes plaster of Paris. When the latter is moistened it again 
combines with water, increases in bulk, and sets to a hard mass. If 
heated much above 260° C, plaster of Paris recombines with water 
only very slowly. 

Calcium phosphate, Ca 3 P 2 8 , forms the greater part of bone. It 
is also found native in Canada as apatite, and in South Carolina as 
" phosphate rock." Coprolites, supposed to be the fossil excreta of 
prehistoric animals, are nearly pure phosphate of calcium. These 
are all largely used in the manufacture of artificial fertilizers or 
superphosphates. 

THE MAGNESIUM GROUP. 
Magnesium : Symbol, Mg. — Atomic weight, 24. — Specific gravity, 1. 748. Melting 

point. 

Zinc: Symbol, Zn. — " " 65.2.— » " 7.146. — 412° C. 

Cadmium: Symbol, Cd.— " " 112. — " " 8.604. —228° C. 

Glucinum: Symbol, Be. — " " 9.3.— " " 2.100. — 900° C. 

These metals all have a valency of 2. They all burn when 
heated in the air, and are ail volatile. They each form but a 
single oxide. Their carbonates are insoluble in water, but are 
dissolved by solution of ammonium carbonate. The metals of this 
group decompose water only very slightly. They dissolve in 
hydrochloric acid with evolution of hydrogen. 

MAGNESIUM. 

Symbol, Mg. — Atomic weight, 24. — Specific gravity, 1.743. 

Magnesium is a white metal, malleable and ductile. It is never 
found native. It oxidizes slowly in damp air. It burns rapidly 



74 GENERAL CHEMISTRY. 

when heated in the air, with a brilliant white light, which may be 
employed instead of sunlight in photography. Magnesium oxide 
or magnesia, MgO, is formed when magnesium is burned. It is 
prepared on a large scale by calcining carbonate of magnesium, 
MgC0 3 , in the same manner as limestone is calcined. Magnesia 
resembles lime, but its hydroxide, MgH 2 2 , is much less soluble 
than hydrate of lime. It forms combinations similar to the corre- 
sponding lime compounds, but its basic properties are less strong 
than those of lime, and most of its compounds are largely soluble 
in water. Epsom salts is magnesium sulphate, MgS0 4 , 7 aq. 1 This 
is soluble in three times its weight of water. Many of the salts of 
magnesium are of importance in pharmacy. Magnesia forms the 
base for the manufacture of bisulphite liquor in the Ekman proc- 
ess for the manufacture of pulp. Silicate of magnesium, with 
small proportions of other metallic silicates, forms a very impor- 
tant class of minerals. Meerschaum, talc, soapstone, serpentine, 
and asbestos are mainly magnesium silicates. 



ZINC. 

Symbol, Zn. — Atomic weight, 65.2. — Specific gravity, 7.146. 

Zinc is a bluish white, hard, lustrous metal. It is rarely found 
native, the best ore being calamine, zinc carbonate, ZnC0 3 . Zinc 
is brittle at low temperatures, but becomes malleable and ductile 
between 100° and 150° C. It .melts at 412° C, and boils at 1040° C. 
It oxidizes very slowly in the air, and hence is employed for coat- 
ing or " galvanizing " iron to protect it from rust. It is readily 
attacked by chlorine and all the mineral acids, and dissolved by 
them. Zinc forms the electro-positive element in most electric 
batteries, the wire leading from it forming the negative pole. 
It is capable of replacing most other metals in solution, itself 
being dissolved ; while the metal originally in the solution is, at 
the same time, deposited in the metallic state. Zinc heated in the 
air burns with a greenish blue flame, forming oxide of zinc, ZnO. 
This is yellow while hot, but on cooling becomes white. Zinc 
hydroxide is a white, gelatinous substance, insoluble in water, but 

1 The abbreviation Aq. for aqua (water) is frequently used to represent a mole- 
cule, IT 2 0, of water which is present as such in association with some other mole- 
cule. 



GLUCINUM. 15 



dissolved by solution of potash or ammonia. Metallic zinc is 
obtained from the oxide by heating with charcoal — - 

2ZnO + C = 2Zn + C0 2 . 

Chloride of zinc, ZnCl 2 , dissolved in water, forms " Burnett's dis- 
infecting solution " of pharmacy. Cellulose or paper treated with 
a strong solution of zinc chloride is changed into a transparent, 
parchment-like substance, vegetable parchment. Sulphate of zinc, 
"white vitriol," ZnS0 4 , 7 aq., is employed in calico-printing as a 
mordant. Zinc carbonate or " zinc white " finds considerable use 
as a substitute for white lead in paint. 



CADMIUM. 

Symbol, Cd. — Atomic weight, 112. — Specific gravity, 8.6. 

Cadmium is a metal much resembling zinc and also tin. It 
accompanies zinc in many of its ores. It melts at 228° C, boils at 
860° C, and is more volatile than zinc. It tarnishes but little in 
the air, but when strongly heated burns to cadmium oxide, CdO. 
Its salts resemble the corresponding salts of zinc, but the metal is 
of little importance either in the metallic state or in combination. 

GLUCINUM. 

Symbol, Be. — Atomic weight, 9.3. — Specific gravity, 2.1. 

Also called beryllium from its being the principal constituent of 
the beryl. It is a white, malleable metal. Called glucinum from 
the Greek word ry\ VK v<;, meaning sweet, on account of the sweet 
taste of solutions of its salts. Its salts resemble both those of zinc 
and aluminum, but are of no importance. The emerald is a double 
silicate of beryllium and aluminum. 



76 GENERAL CHEMISTRY. 



THE EARTH METALS. 



Aluminum : 


Symbol, Al. 


— Atomic 


weight, 27.4. 


Yttrium : 


Symbol, Y. 


u 


92.0. 


Erbium : 


Symbol, E. 


u 


" 168.9. 


Lanthanum : 


Symbol, La. 


I i 


" 139.0. 


Didymium : 


Symbol, D. 


u 


" 144.7. 


Cerium : 


Symbol, Ce. 


— " 


" 138.0. 



These metals are all capable of replacing three atoms of hydrogen 
in combination. Their oxides are earths, and are reduced to the 
metallic state only with great difficulty. From solutions of their 
salts ammonium sulphide precipitates the metal as hydroxide. 

ALUMINUM. 

Symbol, Al. — Atomic weight, 27.4. — Specific gravity, 2.6. 

Aluminum is a bluish white, malleable, and ductile metal, first 
prepared by Wohler in 1827. It is a good conductor of electricity, 
and is very sonorous. It fuses at about 450° C. It does not 
tarnish in the air, but when heated in oxygen it burns with a 
bluish white light, forming the oxide, A1 2 3 . It dissolves in acids, 
with the exception of nitric acid, with moderate facility. Solutions 
of potassium and sodium hydroxides also dissolve it readily with 
the liberation of H2 . The metal is never native, but the oxide and 
silicate are found in abundance, the latter forming the principal 
part of clay. Corundum and emery are native A1 2 3 . 

The sapphire and ruby are also oxide of aluminum, tinted with 
small amounts of other metallic oxides. Bauxite is a hydrous 
oxide of aluminum, containing more or less iron oxide. Aluminum 
possesses properties which would render it a very valuable metal 
for many industrial purposes. The difficulty of reducing its ores 
has, however, up to the present rendered its cost too high to admit 
of its application to any but a few special purposes. 

The price of the metal has, however, been reduced about one- 
half within a couple of years, but it still remains at about $0.65 per 
pound. 

The salts of aluminum are easily prepared from many of its 
natural compounds, and are of great value, especially to the paper 
manufacturer. 



ALUMINUM. 77 



Aluminum hydroxide, A1 2 3 , 3 H 2 0, is precipitated as a nearly 
colorless, translucent jelly when a solution of any aluminum com- 
pound is mixed with a hydrate of an alkali, or alkali-earth metal. 
Hydrate of aluminum, on strong ignition, loses its combined 
water, and is converted into the oxide or alumina, A1 2 3 . 
Hydrate of aluminum or aluminum hydroxide is a moderately 
strong base. It is entirely insoluble in water, but dissolves readily 
in acids to form the corresponding salts. Aluminum chloride, 
AL,Cl 6 ,is not of much importance. Aluminum acetate is of con- 
siderable use as a mordant for fixing the colors, and obtaining 
different shades in dyeing and calico-printing. By far the most 
important of the alumina compounds are the alums. Alums, 
properly so called, are the crystallized double sulphates of 
aluminum and an alkali. Thus potash alum is K 2 A1 2 4 S0 4 , 24 aq., 
and contains 10.92 per cent, of alumina, A1 2 3 , and 45.51 per cent, 
of combined water. Soda alum is Na.AL 4 S0 4 , 24 aq., and con- 
tains 11.23 per cent, of alumina, and 47.11 per cent, of combined 
water. Ammonium alum is (NH 4 ) 2 A1 2 4 S0 4 , 24 aq., and contains 
11.35 per cent, of alumina and 47.63 per cent, of combined water. 
These percentages, of course, represent what the chemically pure 
crystals of these alums contain, and not the " commercially pure " 
article. Sulphate of alumina, Al 2 3 S0 4 , 18 aq., is largely used in 
paper-making instead of true alum, since in the partly dried form 
in which it appears in market it is stronger in alumina than the 
true alums, and at the same time cheaper. This may contain 
from about 15 to about 30 per cent, of alumina, according to the 
completeness with which the combined water has been driven off 
in the manufacture. 

Among the insoluble salts of aluminum may be mentioned 
cryolite, the double fluoride of aluminum, and sodium, which is 
found in large quantities in Greenland, and is employed as a source 
of alumina in alum manufacture ; clay (silicate of alumina) and 
bauxite (hydrate of alumina) are also employed in the manufacture 
of alum and aluminum sulphate. 

The turquoise is a hydrous phosphate of aluminum. 

Manufacture of Alum. — As already indicated, the term "alum" 
in paper-making has come to be almost entirely restricted to sul- 
phate of aluminum, or concentrated alum, as it is often called. 
This material is in this country generally prepared from bauxite. 
The pulverized mineral is added to sulphuric acid of 50° B., con- 



78 GENERAL CHEMISTRY. 

tained in lead tanks. The reaction is very violent, much heat is 
developed, and considerable frothing occurs. After the mixture 
has cooled down it is diluted with water, and allowed to stand to 
deposit silica and other impurities. The clear liquor is decanted 
and run into tanks heated by steam passing through coils of lead 
pipe. The evaporation is continued until a portion of the liquor 
taken up on a stick or rod solidifies in cooling. The concentrated 
material is then run off upon a stone table, where it solidifies, and 
is subsequently broken up and packed. Zinc is sometimes added 
while the alum is in the liquid state, and by its action while dis- 
solving nascent hydrogen is liberated and reduces any iron 
present to the ferrous state, thereby improving the color of the 
product. If sodium bicarbonate is added just before the mass is 
poured, the liberated carbonic acid produces the structure found in 
porous alum. 

In order to produce true potash or ammonia alum, sulphate of 
potash or sulphate of ammonia is added to the clear liquor decanted 
after treatment of the bauxite with acid. The concentration is 
not carried so far as in the manufacture of sulphate of alumina, and 
the alum solution is run into wooden tanks to crystallize. The 
tanks are then knocked down to obtain the crystals. 

When clay is used as the source of alumina, it is moderately 
heated to drive off water, convert the iron to oxide, and render the 
whole mass as porous as possible. 

The powdered clay is added gradually to sulphuric acid of 
50° B., and the whole heated nearly to boiling in lead tanks. The 
mixture gradually thickens, and is run out into iron pans to 
solidify. The sulphate of alumina is washed out with water, and 
cleared by standing. The liquor is then treated in the same man- 
ner as that obtained from bauxite. 

A large quantity of alum for paper-makers' use is made in this 
country from cryolite. By ignition of cryolite with limestone, 
aluminate of soda and calcium fluoride are formed. The former is 
soluble in water, and may be washed out. From this solution 
carbonic acid gas precipitates the alumina, which is then dissolved 
in sulphuric acid to form sulphate of alumina. Another method is 
to boil the cryolite with milk of lime. Aluminate of soda and 
calcium fluoride are formed, and upon addition of a further quantity 
of powdered cryolite the alumina is precipitated and treated with 
acid as before. 



THE IRON GBOUP. 79 



In England alum is largely manufactured from the bituminous 
shale containing iron pyrites and found lying above the coal 
measures. The shale is heaped up and roasted, by which operation 
the pyrites are converted into ferrous sulphate and sulphuric acid, 
both of which react upon the clay, forming sulphate of alumina. 
This may either be dissolved out with water, or the roasted 
material may be transferred to covered pans and heated to about 
110° for two days with sulphuric acid of specific gravity 1.85, while 
ammonia gas is passed into the mixture for the production of 
ammonia alum. Potassium sulphate or chloride, or more often a 
mixture of both, added to the lye from the roasted shale yields 
potash alum. 

YTTRIUM, 

Erbium, lanthanum, and didymium. are all rare metals, found 
principally in Sweden. They never occur native. None of their 
compounds have any industrial importance. 

CERIUM 

Is a little-known metal discovered by Klaproth in 1803. It forms 
two basic oxides, Ce 2 3 and Ce0 2 , and consequently two classes of 
salts, eerie and cerous respectively. Cerium oxalate forms a 
medicinal agent of some importance. Apart from this use cerium 
is of no industrial importance. 



THE IRON GROUP. 
Iron (Ferritin) : Symbol, Fe. — Atomic weight, 56. 



Manganese : Symbol, Mn. — 

Chromium : Symbol, Cr. — 

Cobalt: Symbol, Co. — 

Nickel : Symbol, Ni. — 

Uranium : Symbol, U. — 



55. 
52.2. 

58.8. 
58.8. 
120. 



This group includes the distinctively magnetic metals, and also 
non-magnetic uranium. These metals all decompose water at a 
red heat. Hydrogen sulphide does not precipitate them from their 
slightly acid solutions. 



80 GENERAL CHEMISTRY. 

IRON (Ferrum). 

Symbol, Fe. — Atomic weight, 56. — Specific gravity, 7.844. 

Iron very rarely occurs native. It is sometimes present in the 
metallic state in meteorites, and is found in a mica slate at Canaan, 
Connecticut. Pure iron is an almost silver-white metal, malleable, 
ductile, and very tenacious. It is the most magnetic of all sub- 
stances. It remains unchanged in dry air, and when immersed in 
pure water. In damp air it rusts or oxidizes. Heated in oxygen, 
it burns with vivid incandescence, forming the magnetic oxide, 
Fe 3 4 . Dilute sulphuric and hydrochloric acids dissolve it readily 
with evolution of hydrogen, forming protosulphate, FeS0 4 , and 
protochloride of iron, FeCl 2 , respectively. Dilute nitric acid also 
dissolves it, but the strong acid not only fails to dissolve it but 
renders it "passive," or incapable of being acted upon by other 
acids, until, by appropriate means, its passive condition is altered. 
Bar iron, the purest commercial form, contains from 0.2 to 0.4 per 
cent, of carbon. At a white heat it softens, and may be welded by 
hammering or by strong pressure. In electric welding a small 
portion of the iron is brought to a white heat by the concentration 
on it of a very powerful electric current, and the two surfaces are 
united by strong pressure. Iron melts at about 1530° C. 

The chief ores of iron, in the order of their value, are magnetic 
iron ore or magnetite, Fe 4 , which occurs both massive and crystal- 
line, and from which the purest iron is made by reduction of the ore 
with charcoal alone ; " specular " iron ore, Fe 2 3 ; and red haematite, 
2 Fe 2 3 , 3 aq. This last occurs in two forms, fibrous and compact. 
By roasting it loses its water of combination and becomes Fe 2 3 , 
which is then readily reduced to iron by coal. 

" Spathic " iron ore, carbonate of iron, FeC0 3 , occurs in yellow- 
ish crystals, and also massive. By roasting, carbonic anhydride, 
C0 2 , is driven off and the FeO oxidized to Fe 2 3 . " Clay iron- 
stone " is the chief ore of Great Britain. It is an impure carbonate 
of iron and is reduced in the blast furnace. Blast furnace treat- 
ment is in outline as follows : The ore is mixed with limestone and 
small coal and charged into the top of the furnace, the fires of 
which are urged by a strong blast of air. The ore and the lime- 
stone first roast in the cooler portions of the furnace, and become 
Fe 2 3 and CaO. As the mass sinks down the lime and silica of the 
ore unite to form a fusible slag, while the coal, at the high tempera- 



IRON (FERRUM). 81 



ture, burns at the expense of the oxygen of the Fe 2 3 , reducing the 
latter to Fe, which sinks to the bottom of the furnace in a fluid 
state, and is drawn off from time to time by the removal of a plug 
and allowed to flow into furrows in a bed of dry sand to cool. 
These bars when broken up form " pig iron." 

There are many minor reactions taking place all the while in the 
furnace, which we have not space to notice here. " Pig iron " 
contains from 1 per cent, or less to 5 per cent, and even more of 
carbon, partly or wholly combined with the iron, as well as small 
amounts of sulphide and phosphide of iron. These must be 
removed by different processes of refining, in order to obtain 
" wrought iron." The presence in cast iron of a small amount of 
sulphide or arsenide renders it " hot short," or brittle at a red heat, 
while a small amount of phosphide renders it brittle at the ordinary 
temperature, or "cold short." Steel contains from 0.7 to 1.7 per 
cent, of combined carbon, which gives it its special properties. 

Iron forms four oxides, two of them, FeO, the protoxide, and 
Fe 2 3 , the sesquioxide, being basic ; Fe 3 4 , magnetic oxide, having 
neither basic nor acid properties, and consequently forming no 
compounds; and Fe0 2 , an acid oxide. The last, however, can- 
not be isolated, since when freed from combination it immedi- 
ately evolves oxygen and deposits ferric hydrate. Ferrous oxide, 
FeO, is very unstable, both in its free state and in most of its 
compounds, absorbing oxygen very readily and passing into the 
ferric state. Most of the ferrous salts are soluble in water. 
Ferrous sulphate, "green vitriol," FeS0 4 , 7aq., is also commercially 
called " copperas." It takes this name from the fact of its becom- 
ing reddish brown, coppery, on exposure to the air. It is a sea- 
green, crystalline substance, very soluble in water. Solutions of 
the salt rapidly absorb oxygen and deposit basic ferric sulphate. 

Ferrous bicarbonate, FeC 2 5 , (FeO 2 C0 2 ), occurs in mineral 
waters, called " chalybeate " waters. Such waters, on exposure to 
the air, absorb oxygen and deposit ferric hydrate, 2 Fe 2 3 3 H 2 0. 
A brown bulky precipitate of hydrate, having the composition 
Fe 2 H 6 6 , is obtained when ammonia is added to solutions of ferric 
salts. Ferric oxide or sesquioxide of iron, " iron rust," is Fe 2 3 . It 
combines with acids to form ferric salts. Most of these are very 
soluble. Ferric chloride, Fe 2 Cl 6 , may be obtained by sublimation 
in brown scales, which very rapidly absorb water from the air and 
deliquesce, or liquefy, to an orange-red solution. Ferric nitrate, 



82 GENERAL CHEMISTRY. 

Fe 2 6 N0 3 , 12 aq., is very soluble. In conjunction with tannins it 
forms a black dye. Ferric oxide may take the place of alumina, 
ALO3, in the formation of ferric alum: thus K 2 Fe 2 4 S0 4 , 24 aq., is 
potash ferric alum. Ferric oxide has received a curious applica- 
tion in the manufacture of caustic soda from soda-ash, sodium 
carbonate. When ferric oxide is furnaced at a low red heat with 
soda-ash, a compound of the iron and soda, probably sodium ferrate, 
Na 2 Fe0 2 , is formed, from which hot water extracts sodium hydrate, 
NaHO, leaving ferric oxide, which has but to be dried to be again 
ready for use in the same operation. 

Ferrous salts are very readily changed into the corresponding 
ferric salts by means of oxidizing agents, as by boiling with nitric 
acid, or, in the cold, by hypochlorites, etc. ; and, conversely, ferric 
salts are readily changed to ferrous salts by reducing agents, such 
as nascent hydrogen, hydrogen sulphide, sulphurous acid, etc. 

MANGANESE. 

Symbol, M11. — Molecular weight, 55. — Specific gravity, 8.01. 

Manganese is a grayish white, brittle metal, never occurring 
native. It was discovered by Gahn in 1774. The metal oxidizes 
rapidly in the air, and decomposes water slowly at the ordinary 
temperature. It is prepared from manganous carbonate, MnC0 3 , 
by heating to whiteness in a smith's forge with charcoal. The 
metal alloys readily with iron to render the latter harder and more 
elastic. Manganese occurs in a variety of combinations. Its most 
valuable ore is pyrolusite, Mn0 2 . 

Manganese forms two basic, two indifferent, and two acid oxides. 
Manganese oxide, MnO, is an olive-green substance, which when 
ignited in the air absorbs oxygen and is changed into brown 
manganous-manganic oxide. Manganous oxide is a powerful base. 
Most of its salts are pink or rose red. 

Manganic oxide, Mn 2 3 , occurs in a natural form as manganite. 
It is a feeble base. It may be substituted for alumina and ferric 
oxide in alums and other compounds. This oxide gives a violet 
color to glass, and the color of the amethyst is also due to the same 
substance. 

Manganous-manganic oxide, Mn 3 4 , is formed by the ignition of 
any of the other oxides of manganese with free contact of air. It 
is not basic. 



COBALT. 83 

Manganese dioxide or peroxide, Mn0 2 , is the most useful ore of 
manganese. It is not basic. When strongly ignited it gives off 
oxygen, and is converted into Mn 3 4 . When heated with sulphuric 
acid it also evolves oxygen. When heated with hydrochloric acid 
chlorine is given off, and manganous chloride is formed according 
to the equation — ■ 

4 HC1 + Mn0 2 = Cl 2 + MnCL + 2 H 2 0. 

Manganic acid, H 2 Mn0 3 (the anhydride being Mn0 2 ), is green. 
The manganates are very unstable. Their solutions, as well as 
those of the permanganates, form powerful disinfectants. 

Permanganic acid, H 2 Mn 2 7 (anhydride, Mn 6 ), is scarcely 
known except in combination. Potassium permanganate, K 2 Mn 2 7 , 
is a dark purple salt, crystallizing in needles. It yields up a por- 
tion of its oxygen very readily to oxidizable substances, being at 
the same time reduced to Mn0 2 or MnO. Its use as a bleaching 
agent has been proposed, and as such it is very effective under 
favorable conditions, but the expense of the substance and of 
its use has hitherto prevented its extensive emplo} T ment for this 
purpose. 

Solutions of permanganates form very efficient deodorizers and 
disinfectants. The oxides of manganese and many of its salts find 
extended application in the arts. 

COBALT. 

Symbol, Co. — Atomic weight, 58.5. — Specific gravity, 8.95. 

Cobalt is a reddish white, brittle metal, difficultly fusible. It is 
magnetic and very tenacious. It was discovered by Brandt in 
1733. The best ore of cobalt is the arsenide, As 2 Co, or speiss- 
cobalt. Cobalt forms two oxides, cobaltous oxide, CoO, of a 
greenish color, and cobaltic oxide, Co 2 3 , which is black. The 
former is used as a pigment. "Smalt" is a glass colored blue by 
cobaltous silicate. The salts of cobalt are blue, pink, and red. 
Unsized paper which has been impregnated with a solution of cobalt 
chloride is blue in dry weather, but turns pink when exposed to a 
moist atmosphere. Such papers, made up into various fanciful 
articles, are sold in France as a sort of weather indicator. 



84 GENERAL CHEMISTRY. 

NICKEL. 

Symbol, Ni. — Atomic weight, 58.8. — Specific gravity, 8.8. 

Nickel is a hard, bluish white, difficultly fusible metal, capable 
of receiving a high polish. It is tenacious in a high degree. Nickel 
nearly always accompanies cobalt in its ores. It also resembles 
the latter in many respects. The chief ores of nickel are the 
arsenide or " Kupfer-nickel," As 2 Ni 2 , the diarsenide, As 2 Ni, and the 
arsenio-sulphide, AsNiS. The metal is obtained by the ignition of 
nickel oxalate in a wind furnace, or by reducing the oxide by igni- 
tion with carbon. Nickel is magnetic at the ordinary temperature, 
but loses this property at 350° C. It is not easily acted on by 
acids, with the exception of nitric acid. " German silver " is an 
alloy of copper, zinc, and nickel, being practically Cu 5 Zn 3 Ni 2 . 

Nickel forms one basic oxide, nickel oxide, NiO, and an indiffer- 
ent oxide, nickel peroxide, Ni 2 3 . The caustic alkalis precipitate 
nickel hydroxide, NiH 2 2 , from solutions of nickel salts, as a bulky, 
light green precipitate, insoluble in potash and soda, but soluble in 
ammonia to a blue solution. The latter solution has the property 
of dissolving silk, while it does not dissolve cellulose. 



CHROMIUM. 

Symbol, Cr. — Atomic weight, 52.2. — Specific gravity, 6.81. 

Chromium is a steel-gray metal, more intractable than platinum. 
It was discovered by Vauquelin in 1797. It is insoluble even in 
aqua regia. 1 Never native. The metal may be obtained by strong 
ignition of the oxide with charcoal in a wind furnace. Chromium 
forms two basic oxides, chromous oxide, CrO, and chromic oxide, 
Cr 2 3 . The latter is a green, earthy substance, often employed as 
a pigment and to give a green color to jDorcelain and glass. It 
gives to the emerald and to serpentine their characteristic colors. 
Chromic oxide may replace alumina in the formation of alums. 

Chromium also forms an acid oxide, Cr0 3 , chromic anhydride, 
which forms brilliant, dark red deliquescent prisms. Chromic 
acid, H 2 Cr0 4 , is the most important compound of chromium. 
With potash it forms neutral chromate, K 2 Cr0 4 , yellow, and the 

1 This is only true of the crystallized metal obtained by Fremy. 



TIN. 85 

bichromate or red chromate, K 2 Cr 2 7 . Chromic yellow or canary 
yellow is neutral lead chromate, PbCr0 4 . It is formed when a 
solution of a chromate is added to a solution of acetate of lead. 
Orange mineral is basic lead chromate, PbCr0 4 , PbO. 

The compounds of chromium, in which the latter takes the part 
of base, are of little importance. They are all remarkable, as well 
as the chromates, for the beautiful colors of the salts themselves, 
and also of their solutions. 

URANIUM. 

Symbol, Ur. — Atomic weight, 120. — Specific gravity, 18.4. 

Uranium is a steel-gray, slightly malleable metal, never found 
native. It is not oxidized at ordinary temperatures, but burns 
when strongly heated. In its chemical properties, as also in most 
of its compounds, it bears a close analogy to iron and manganese. 
The ores of uranium are of rare occurrence, and the element is of 
little practical importance. 



THE TIN GROUP. 

Tin (Stannum) : Symbol, Sn. — Atomic weight, 118. 
Titanium: Symbol, Ti. — " " 50. 

Zirconium: Symbol, Zr. — " " 89.5. 

Thorium: Symbol, Th.— " " 231.5. 



TIN. 

Symbol, Sn. — Atomic weight, 118. — Specific gravity, 7.292. 

Tin is a lustrous, white, malleable metal, never found native. 
It possesses but little ductility. It has a slight but peculiar odor. 
When a bar of tin is bent it emits a peculiar crackling sound, 
called the "cry" of tin. Tin melts at 228° C. When strongly 
heated in the air it burns into stannic oxide, Sn0 2 . At ordinary 
temperatures it tarnishes slowly. Hydrochloric acid dissolves tin 
slowly, forming stannous chloride, SnCl 2 . ' Boiling sulphuric acid 
dissolves it to stannic sulphate. Nitric acid does not dissolve tin, 
but changes it into insoluble metastannic acid, H 2 Sn 3 O n , 4aq. 
Tin is a very valuable metal for many purposes, both in the pure 
form and as alloyed with other metals. Pewter is four parts tin 



86 GENERAL CHEMISTRY. 

and one part lead. Common solder is usually equal parts tin and 
lead. Bronze is an alloy of copper and tin. " Phosphor bronze " 
contains a little phosphide of tin, to which its peculiar properties 
are due. 

Tin forms two oxides : stannous oxide, SnO, a black, crystal- 
line substance which rapidly absorbs oxygen, and becomes stannic 
oxide, Sn0 2 ; stannous hydroxide, SnH 2 2 , is white and gelati- 
nous, very soluble in solutions of caustic potash and soda. It is a 
powerful base. 

Stannic oxide, Sn0 2 , is a yellowish white, insoluble substance. 
This is found as cassiterite or tinstone, and forms the chief ore of 
tin. 

Stannic acid, H 2 Sn0 3 , is formed as a white gelatinous precipitate, 
by adding ammonia to a solution of stannic chloride. It is insolu- 
ble in ammonia, but forms compounds with the alkali and alkali 
earth metals, called stannates. Stannate of soda is Na 2 Sn0 3 , 3 aq. 

Stannous sulphide, SnS, is a bluish gray substance, formed hv 
fusing together tin and sulphur. The same substance is precipi- 
tated as a brown rated sulphide by passing hydrogen sulphide 
into a solution of stannous chloride. " Mosaic gold " is stannic 
sulphide, SnS 2 . The soluble salts of tin are largely used in dyeing 
as mordants. 

TITANIUM. 

Symbol, Ti. — Atomic weight, 50. — Specific gravity, 5.3. 

Titanium is a rare element, never native. The chief ore is 
titanic anhydride, Ti0 2 , occurring as "Rutile," " Brookite," and 
" Anatase." Titanium forms comparatively few compounds, and is 
of little interest. It was discovered by Gregor in 1791. 

ZIRCONIUM. 

Symbol, Zr. — Atomic weight, 89.5. — Specific gravity, 4.15. 

Zirconium is a black amorphous powder, assuming some lustre 
under the burnisher. It resembles silicon and titanium, and under 
certain circumstances antimony. 



TUNGSTEN (WOLFE AM). 87 

THORIUM. 

Symbol, Th. — Atomic weight, 231.5. — Specific gravity, 7.7 to 7.9. 

Thorium is a metal discovered by Berzelius in 1828. The 
metal dissolves easily in nitric acid, and slowly in hydrochloric 
acid. It forms one oxide, which is white and very heavy. Tho- 
rium is of no importance in the arts. 

MOLYBDENUM. 

Symbol, Mo. — Atomic weight, 96. — Specific gravity, 8.62. 

Molybdenum is a white, brittle metal, very difficultly fusible. It 
takes its name from the Greek word /u,o\v/38aiva, a piece of lead, 
which its chief ore, molybdenite, resembles. 

It forms two basic and one acid oxides. The basic oxides are 
molybdous oxide, MoO, black, and molybdic oxide, Mo0 2 , dark 
brown. In solutions of salts of molybdic oxide, alkalis precipitate 
molybdic hydroxide. The latter is readily soluble in acids giving 
red-colored solutions. Nitric acid changes molybdic oxide to molyb- 
dic anhydride, Mo0 3 , which may unite with water to form molybdic 
acid, not known, however, in the free state. Neither the metal nor 
its salts are of much technical importance. Some of the molybdates 
of the alkalis are useful in the laboratory for the detection and 
separation of phosphoric and arsenic acids and the precipitation of 
certain alkaloids. 

TUNGSTEN (Wolfram). 

Symbol, W. — Atomic weight, 184. — Specific gravity, 17.6. 

Tungsten is an iron-gray metal, nearly infusible. Its most com- 
mon ore is wolfram, tungstate of iron and manganese. It is a 
difficult metal to obtain in the free state, but may be alloyed 
with some difficulty with other metals by simultaneous reduction 
of the oxides. It forms a variety of compounds with oxygen, some 
of them exhibiting acid, and others basic properties. Sodium tung- 
state possesses the property of rendering cotton fabric, etc., unin- 
flammable. 



GENERAL CHEMISTRY 



THE ANTIMONY GROUP. 

Antimony : Symbol, Sb. — Atomic weight, 122.0. 

Arsenic: Symbol, As. — " " 75.0. 

Bismuth: Symbol, Bi. — " " 210.0. 

Vanadium: Symbol, Va. — " " 51.3. 

Niobium: Symbol, Nb.— " " 94.0. 

Tantalum: Symbol, Ta. — " " 182.0. 



ANTIMONY. 

Symbol, Sb. — Atomic weight, 122. — Specific gravity, 6.75. 

Antimony is a brilliant, bluisli white metal, crystalline, and so 
brittle that it may be powdered in a mortar. It melts at 450° C, 
and in the air burns brilliantly with the formation of antimonous 
oxide, Sb 2 3 . Strong hydrochloric acid dissolves the metal slowly, 
forming antimonous chloride, SbCl 3 . In chlorine gas the metal 
takes fire, and burns to SbCl 3 . Nitric acid converts it into 
antimonic acid, HSb0 3 . Antimony alloys readily with most other 
metals. Type metal consists of two parts lead, one part tin, and 
one part antimony, the latter being added to give hardness and 
stiffness to the type, and also to cause the metal to expand in cool- 
ing, and so take the fine lines of the mold. "Britannia metal'' is 
nine parts tin and one part antimony. Antimonous hydride, or 
stibine, H 3 Sb, is formed when hydrogen is liberated by zinc and 
acid in the presence of any compound of antimony. It is a color- 
less, fetid gas, which burns with a greenish flame to water and 
antimonous oxide ; or, when the supply of air is insufficient, to water 
and antimony. 

Antimony forms with chlorine antimonous chloride, SbCl 3 ; anti- 
monous oxychloride, SbCIO ; and antimonic chloride, SbCl 3 . Anti- 
monous sulphide, Sb 2 S 3 , is of a beautiful orange color. Antimonic 
sulphide, Sb 2 S 5 , is also orange red. 

Antimonous oxide, Sb 2 3 , occurs native as " white antimony ore.*' 
It is a gray white crystalline powder, becoming yellow on heating. 
It is soluble in hydrochloric acid, and in tartaric acid solution to 
form chloride or tartrate of antimony. The latter is the "tartar 
emetic " of the pharmacists. When heated in the air antimonous 
oxide burns to antimonous antimonate, Sb 2 4 . 



VANADIUM. 89 



Antimonic anhydride, Sb 2 5 , is a pale yellow, tasteless, insoluble 
powder. United with water it forms antimonic acid, HSb0 3 . 

Sb,0 5 + H 2 = 2HSb0 3 . 

It forms antimonates with the basic oxides. Metantimonic acid 
is H 4 Sb 2 7 . Metantimonate of sodium is interesting as being the 
only compound of sodium with an inorganic acid which is insoluble 
in water. 

Antimony and its compounds bear a close analogy to the corre- 
sponding forms of arsenic. These two metals appear to stand, as it 
were, on the border line between the metals and the non-metallic 
elements. Antimony, however, has the metallic character more 
distinctly than arsenic. Both have the property of rendering other 
metals with which they are alloyed hard and brittle. 

Arsenic has been previously noticed under the non-metallic 
elements. 

BISMUTH. 

Symbol, Bi. — Atomic weight, 210. — Specific gravity, 9.79. 

Bismuth is a beautiful crystalline metal, of a reddish white hue. 
It melts at 264° C. When strongly heated in chlorine gas bismuth 
burns with a bluish flame, forming the terchloride, BiCl 3 . Bismuth 
has the property of lowering to a remarkable degree the melting- 
point of alloys of which it forms a part. Fusible metal is an alloy 
of eight parts bismuth, five parts lead, and three parts tin. This 
alloy melts at 98° C. 

Similar alloys, made in such proportions that they fuse at some 
particular temperature, are used as safety plugs in boilers and for 
certain joints in automatic sprinklers. Except in such alloys 
metallic bismuth is little used. It forms four oxides. Some of its 
salts are medicines of importance, especially the nitrate, which is 
also used for giving a colorless iridescent glaze to porcelain. 



VANADIUM. 

Symbol, V. — Atomic weight, 51.3. — Specific gravity, 5.5. 

Vanadium is a very rare metal, discovered by Sefstrom in 1830, 
and never found native. In its combinations with. oxygen it is 



90 GENERAL CHEMISTRY 



analogous to nitrogen, forming five oxides, — V 2 0, V 2 2 , V 2 3 , 
V 2 4 , and V 2 O s . The highest of these, V 2 5 , forms with water 
vanadic acid, HV0 3 , and the salts of this acid are the only com- 
pounds which have received any industrial application. Vanadium 
in solution is remarkable for its affinity for cellulose, this substance 
being able to abstract vanadium from a solution containing only 
one part of the metal in a trillion. 

Blitz has patented a process for reducing wood to pulp by the 
use of a solution of sodium sulphide, containing, to every cord of 
wood, fifteen grains of vanadate of ammonia dissolved in hydro- 
chloric acid. We cannot believe that the efficiency of the solu- 
tion is in any way increased by this homoeopathic addition. 

NIOBIUM. 

Symbol, Nb. — Atomic weight, 94. — Specific gravity, 4.06. 

Niobium is a rare element, never native. It is sometimes called 
Columbium, on account of its having been first discovered by Hatch- 
ett in columbite in 1801. It greatly resembles phosphorus in its 
combinations. 

TANTALUM. 

Symbol, Ta. ■ — Atomic weight, 182. 

A rare metal, about whose properties little is known. Discov- 
ered by Ekeberg in the mineral called tantalite. 



THE LEAD GROUP. 

Symbol. Atomic weight. Specific gravity. Fusing-point. 



Lead: 


Pb. 


207.0 


11.38 


325° C. 


Thallium : 


Tl. 


203.6 


11.86 


294° C. 


Copper : 


Cu. 


63.4 


8.95 


1091° C. 


Gallium : 


Ga. 


68.0 


5.90 


30.1° C. 


Indium : 


In. 


113.4 


7.40 


176° C. 



LEAD (Plumbum). 

Symbol, Pb. — Atomic weight, 207. — Specific gravity, 11.38. 

Lead is a bluish-colored metal, soft, malleable, and ductile, but 
little tenacious. It tarnishes slowly in moist air. It is acted 
upon to a considerable extent by soft water in the presence of air 



LEAD {PLUMBUM). 91 



and carbonic acid, also by water containing chlorides and nitrites. 
Hard water and that containing sulphates does not attack lead. 
Hence lead poisoning need not be feared from the use of water 
which contains sulphates. Lead oxidizes rapidly when melted in 
the air, forming the yellow oxide, PbO, litharge. On further 
heating litharge takes on more oxygen and becomes red lead or 
minium, Pb 3 4 , sometimes called "orange mineral." At a still 
higher temperature red lead loses oxygen, and is changed back to 
litharge. Two other oxides of lead are known : the suboxide, 
Pb 2 0, which is black, and the peroxide, Pb0 2 , which is brown. 

Lead is never found native. Its chief ores are galena, lead 
sulphide, which usually carries more or less silver sulphide, and 
the peroxide known as "heavy lead ore," or puce lead. Lead 
expands with heat, like other metals, but is peculiar in that it 
does not return to its former dimensions on cooling, a bar or sheet 
of the metal growing continually larger and correspondingly thinner 
with each successive heating and cooling. On this account in 
a boiler lined with lead the lining soon becomes too large for the 
shell, and either breaks or wrinkles at the weakest points after a 
certain number of heatings and coolings. 

Dilute sulphuric and hydrochloric acids have scarcely any action 
on lead. Chemically pure lead is, however, attacked to a greater 
extent than that containing traces of other metals. It resists the 
action of sulphurous acid perfectly, and consequently is of great 
value in the sulphite process. 

Nitric acid dissolves it readily, forming nitrate of lead, Pb(N0 3 ) 2 . 
Strong sulphuric acid scarcely attacks lead at moderate tempera- 
tures, but at about 300° C. it dissolves it so rapidly as to almost 
produce explosion. Sulphate of lead, PbS0 4 , is a white, insoluble 
substance. It is formed when sulphuric acid or a soluble sulphate 
in solution is added to the solution of a soluble lead compound. 
Hence Glauber's salts, sulphate of soda, or " Epsom salts," sul- 
phate of magnesia, are the antidotes for lead poisoning. " Sulphu- 
ric acid lemonade," which is water soured by sulphuric acid and 
flavored with lemon, is used by workmen employed in white lead 
works as a preventive of lead poisoning. Sulphate of lead is fre- 
quently employed as an adulterant of " white lead," which is the 
basic carbonate of lead, PbH 2 2 , 2 PbCO ? , . The normal carbon- 
ate is PbC0 3 . 

All adulterants of white lead injure its qualities as a paint. 



92 GENERAL CHEMISTRY. 

Nitrate of lead Pb. (N0 3 )" is a white crystalline substance soluble 
in eight parts of water. Acetate or " sugar " of lead, Pb (C 2 H 3 2 ) 2 , 
3 aq., is soluble in twice its weight of water. Chromate of lead, 
chrome yellow, PbCr0 4 , is formed when a solution of bichromate 
of potash or soda is added in excess to a solution of acetate of 
lead as a beautiful yellow precipitate entirely insoluble in water. 
By boiling the yellow chromate of lead with limewater, a portion 
of the chromic acid combines Avith the lime, leaving basic lead 
chromate, Pb 2 Cr0 5 (or PbO, PbCr0 4 ), which is an orange red, 
almost approaching vermilion. This is also sometimes called 
orange mineral. Flint glass is a silicate of lead and potash. 
" Paste " for imitation gems is also a silicate of potash and lead, 
containing more lead than flint glass. 

THALLIUM. 

Symbol, Tl. — Atomic weight, 203.(3. — Specific gravity, 11.80. 

Thallium is a soft, malleable, crystalline metal, between lead 
and silver in color. It was discovered by the aid of the spectro- 
scope, in 1861, by Crooks. Thallium melts at 294° C. It tar- 
nishes in moist air. Heated in oxygen to 315° C, it burns with 
a green light. It greatly resembles lead in its properties, and also 
in its compounds. It has found scarcely any useful applications. 
Thallium compounds are poisonous. 

COPPER (Cuprum). 

Symbol, Cu. — Atomic weight, 63.4. — Specific gravity, 8.95. 

Copper is a metal of a rich reddish color, of ten. found native, 
notably near Lake Superior, where it occurs sometimes in masses 
of tons' weight, and often containing native silver. Copper is one 
of the most useful of metals. It is malleable, ductile, and tena- 
cious to a high degree. Next to silver it is the best conductor 
of heat and electricity. It corrodes but slowly, and only super- 
ficially, in moist air. Seawater, however, acts upon it rapidly. 
Copper melts at 1091° C. Heated to redness in the air it oxidizes 
rapidly, forming first red cuprous oxide, Cu 2 0, and then cupric 
oxide, CuO. 

Dilute hydrochloric and sulphuric acids attack copper scarcely 
at all in the cold. Sulphurous acid (moist) corrodes it rapidly. 



COPPER (CUPRUM). 93 



Nitric acid attacks it immediately. Boiled with strong sulphuric 
acid, copper is slowly dissolved as copper sulphate, and at the 
. same time sulphurous acid gas, S0 2 , is given off according to the 
equation- ^ + g ^^ = ^^ + ^ + g ^ 

This reaction furnishes a convenient means of preparing sulphurous 
anhydride, S0 2 , in the laboratory. Chlorine gas combines rapidly 
with copper, so that copper foil immersed in chlorine takes fire 
or becomes incandescent from the heat generated by the rapid 
chemical combination. Copper alloys readily with many of the 
metals. Brass is an alloy of zinc and copper ; bell metal and bronze, 
tin and copper, etc. 

Copper burns with a green flame in the oxyhydrogen flame. 
Its salts also impart a green color to flame. 

Copper forms two basic oxides : cuprous oxide, Cu 2 0, red; cupric 
oxide, CuO, black. The former occurs native as "ruby copper 
ore." It gives a ruby color to glass. The cuprous salts are color- 
less in solution. They are few in number, and of little importance 
in the present connection. 

Cupric oxide or, as ordinarily spoken of, copper oxide, CuO, is 
black, and forms with acids green or blue salts. Ordinary " blue- 
stone," or "blue vitriol," is cupric sulphate, CuS0 4 , 5 aq. It is 
soluble in four parts of water, forming a blue solution. At 200° C. 
all the water of crystallization, or combined water, is driven off, 
and the salt becomes white. 

Cupric chloride, CuCl 2 , 2 aq., forms green deliquescent needles. 

Cupric acetate, Cu(C 2 Ha0 2 )2, H 2 0, crystallizes in green prisms. 
Verdigris is a mixture of several basic cupric acetates, and occurs 
in both a green and blue variety. 

Insoluble salts are the carbonate, the arsenite and arsenate, and 
the aceto-arsenite, the latter being known as " Paris green." 

Cupric oxide is soluble in oils and fats, which may become 
poisonous through its presence. It, however, colors them green. 
It also gives a green color to glass. 

Ammonia, added in small quantity to solutions of cupric salts, 
precipitates the copper as cupric hydrate, CuH 2 5 , of a light green- 
ish blue color. Excess of ammonia redissolves the cupric hydrate 
to a beautiful deep blue solution. Copper is precipitated from its 
solutions by iron, zinc, and many other metals, either in a spongy 
form or as a coating or plating on the surface of the immersed 



94 GENERAL CHEMISTRY. 

metal. An easy test for the presence of copper in a solution is 
to immerse in it a piece of polished steel, as a knife-blade, when, 
if even a small amount of copper is present, the steel will, after a 
short time, show the characteristic color of copper. 

Copper forms the best material for conductors and pipes of a 
paper-mill, as the alum used serves to keep the inside of the pipes 
clean and bright, and slime is less likely to rind a lodgment than 
on other metals. 

GALLIUM. 

Symbol, Ga. — Atomic weight, 68. — Specific gravity, 5.9. 

Gallium is a hard, white metal, resembling aluminum and zinc. 
It was discovered by Lecoq de Boisbaudran in a zinc blende in 
1875. It melts at 30.1° C. Heated to redness, it only oxidizes 
on the surface. Gallium oxide may be substituted for alumina in 
alums. 

The metal and its compounds have yet found no practical uses. 
It is of infrequent occurrence. 

INDIUM. 

Symbol, In. — Atomic weight, 113.4. — Specific gravity, 7.42. 

Indium is a rare metal, never found native. It was discovered 
in 1863 in a German zinc ore. It is a white metal, malleable and 
ductile. It melts at 176° C. When heated to redness in the air 
it burns with a beautiful violet-colored flame, forming indium 
sesquioxide, ln 2 3 , which is yellow. Zinc or cadmium (metallic) 
immersed in a solution of indium replaces the latter and precipitates 
metallic indium. 



SILVER (ARGENTUM). 95 



THE SILVER GROUP. 
Sometimes called the Noule Metals. 

Symbol. Atomic weight. Specific gravity. Fusing-point. 



Silver : 


Ag. 


108.0 


10.53 


916° C, 


Mercury : 


Hg. 


200.0 


13.59 


38.8° C 


Gold: 


Au. 


196.6 


19.34 


1037° C 


Platinum : 


Pt. 


197.1 


21.53 


1460° C 


Palladium : 


Pd. 


106.5 


11.80 


1360° C, 


Rhodium : 


Eh. 


104.3 


12.10 




Ruthenium : 


Ru. 


104.2 


11.40 




Osmium : 


Os. 


199.0 


22.48 




Iridium : 


Ir. 


198.0 


21.15 





SILVER (Argentum). 

Symbol, Ag. — Atomic weight, 108. — Specific gravity, 10.53. 

Silver is frequently found native both in the crystalline and 
massive forms. It is the whitest and most lustrous of all the 
metals, also the best conductor of heat and electricity. It does not 
tarnish in pure air. Its oxide is reduced to metal by heat alone. 
Silver melts at 916°. When melted the metal will absorb twenty- 
two times its bulk of oxygen ivithout combining with it. On cool- 
ing the absorbed oxygen is discharged, often with some violence, 
causing " sprouting " and " spitting " of the metal. 

Silver has a great affinity for sulphur, being rapidly blackened 
and converted into sulphide of silver by free sulphur or soluble 
sulphides. Sulphuric and hydrochloric acids scarcely attack silver 
at all. It is, however, rapidly attacked by nitric acid, and dis- 
solved with the formation of nitrate of silver, AgNO ;J . Silver 
readily alloys with other metals. Silver coins are usually alloys of 
silver and copper or nickel. 

Silver forms three oxides, only one of which is basic : — 

Argentous oxide, Ag 4 0, a very unstable compound ; 

Argentic oxide, Ag 2 0, which is a brown substance, a powerful 
base. It is soluble in ammonia, and slightly soluble in water. At 
a low red heat it is decomposed into metal silver and oxygen. 

The peroxide, Ag 2 2 , is formed in dark gray needles by the 
electrolysis of silver nitrate. 

Argentic sulphide, Ag 2 S, occurs native as " silver glance." The 



96 GENERAL CHEMISTRY. 



same substance is formed when hydrogen sulphide or an alkaline 
sulphide is added to a solution of silver. 

Nitrate of silver, AgN0 3 , is made by dissolving silver in dilute 
nitric acid, evaporating the solution, and crystallizing. It thus 
forms colorless anhydrous tabular crystals. The crystals melt at 
219° C, and the mass may then be cast into sticks, which form the 
" lunar caustic " of pharmacy. Nitrate of silver is very soluble in 
water, and readily so in alcohol. Other soluble salts of silver are 
the sulphate, Ag 2 S0 4 ; silver alum, Ag 2 Al 2 4 S0 4 , 24 aq.; acetate, 
AgC 2 H a 2 ; fluoride, AgF ; and the double cyanide of silver and 
potassium, 2 KCN, AgCN, H 2 0. The latter is the salt commonly 
employed in silver-plating. 

All the soluble silver salts are irritant poisons. Their antidote 
in all cases is common salt, NaCl. 

All salts of silver, except those enumerated above, are nearly or 
quite insoluble in water. The chloride, bromide, and iodide of 
silver are peculiarly sensitive to light, turning nearly black on 
short exposure to sunlight. 

The art of photography depends upon the sensitiveness of the 
silver salts to light. The '" plate " is prepared by spreading a film 
of albumen, collodion, or gelatine, carrying the bromide and iodide 
of silver, upon glass. When the plate is exposed to light, as in 
the camera, obscure chemical changes take place which affect the 
subsequent solubility of the salts in the fixing or reducing bath. 
The extent of the change is proportional to the amount of light 
falling upon different portions of the plate. The image is sub- 
sequently developed by contact with a reducing agent, as, for 
instance, a solution of ferrous sulphate, which converts those por- 
tions of the silver salts which have been affected by light into 
metallic silver. The image is fixed or rendered permanent by 
washing out the undecomposecl silver salts by a solution of sodium 
thiosulphate ("hyposulphite of soda"). If, now, paper, similarly 
prepared to the glass plate, is exposed to light under this " nega- 
tive," the silver salts are blackened where the light comes through 
the negative, and the " positive " picture so obtained may be fixed 
by washing in a bath of sodium thiosulphate. Paper made for 
photographic purposes should be free from acid, antichlors, and 
bleach, since these affect the sensitive silver salts. 



MERCURY (HYDRARGYRUM). 97 

MERCURY (Hydrargyrum). 

Symbol, Hg. — Atomic weight, 200. — Specific gravity, 13.59. 

Mercury is the only metal known which is fluid at the ordinary 
temperature of the air. It freezes or solidifies at — 38.8° C. Mer- 
cuiy is rarely found native, more frequently as cinnabar, mercuric 
sulphide, HgS. It does not tarnish, and its oxides are reduced by 
heat alone ; hence it is called a " noble metal." It boils at 357° C, 
and ma}^ be readily distilled. 

Mercury readily alloys with other metals. Alloys of mercury 
are called amalgams. It amalgamates with gold with extreme 
facility, dissolving the latter almost as readily as water dissolves 
sugar. Advantage is taken of this property in the extraction of 
gold from gold-bearing quartz, the gold being dissolved out from 
the powdered rock by means of mercury, and the resulting amal- 
gam distilled in iron retorts, when the gold remains in the retort 
and the mercury in the receiver may be used again. The amalgam 
of tin and mercury is employed for " silvering " mirrors. At 300° C. 
mercury slowly oxidizes, forming mercuric oxide, HgO. Hydro- 
chloric acid does not attack mercury. Nitric acid dissolves it in 
the cold to mercurous nitrate, Hg 2 N 2 6 , and, when heated, to mer- 
curic nitrate, HgN 2 6 . Heated with sulphuric acid, sulphurous 
acid gas, S0 2 , is given off, and the metal is dissolved to mercuric 
sulphate, HgS0 4 . 

Mercury forms two oxides, both basic. Mercurous oxide, Hg 2 0, 
is black and unstable. It forms with acids mercurous salts. Mer- 
curic oxide, HgO, is a red crystalline powder. Mercuric oxide 
forms with acids mercuric salts. 

Calomel is mercurous chloride, Hg 2 Cl 2 . Corrosive sublimate 
is mercuric chloride, HgCL . The former is almost entirely insol- 
uble in water and alcohol, while the latter is very readily soluble 
in both. All the soluble salts of mercury, as well as such other 
of its compounds as may become in any degree soluble in the 
system, are violent acrid poisons. Their antidote is raw egg albu- 
men, or white of egg. True vermilion is an artificial mercuric 
sulphide, Hg 2 S. Mercuric iodide, HgL, is also of a vivid scarlet 
color. " Turpeth mineral " is yellow, and consists of basic mer- 
curic sulphate, HgS0 4 , 2 HgO. 

All the mercuric salts are powerful destroyers of organic life, 
and hence are frequently of the highest use as disinfectants. One 



98 GENERAL CHEMISTRY. 



part of corrosive sublimate in 5000 of water has been found to 
destroy instantly all forms of bacteria. 

GOLD (Aurum). 

Symbol, Au. — Atomic weight, 196.0. — ■ Specific gravity, 19.34. 

Gold is always found native. It is very widely distributed, but 
occurs only in comparatively small quantities. It is a bright yel- 
low, lustrous metal, the most malleable and ditctile of all the 
metals. Gold leaf is often only towoo- °f an mcn m thickness. 
It melts at 1037° C. It does not tarnish in the air, and its oxide 
is reduced by heat alone. It is not attacked by any single acid, 
but is readily dissolved as auric chloride, AuCl 3 , by aqua regia 
(hydrochloric acid three parts, to nitric acid one part). It is 
also attacked by chlorine, bromine, and iodine. 

Pure gold is a very soft metal, and hence is alloyed with a per- 
centage of copper, which renders it much harder and better able 
to resist wear. As a conductor of heat and electricity, gold is not 
so good as silver and copper. 

The compounds of gold are of little importance, since they are 
only used for a few special purposes, as, e. g., gilding porcelain, etc. 

PLATINUM. 

Symbol, Pt. — Atomic weight, 197.1. — Specific gravity, 21.53. 

Platinum is a white, lustrous metal, resembling tin in appear- 
ance, very malleable and ductile. It was discovered in 1741. It 
does not tarnish in the air, and is attacked by no single acid. 
Aqua regia dissolves it slowly as platinum chloride. It is also 
attacked and dissolved slowly by chlorine, bromine, and iodine in 
presence of water. Platinum always occurs native and alloyed 
with palladium, osmium, iridium, rhodium, and ruthenium. It has 
been found in greatest quantity in the Ural Mountains, but even 
there it is by no means abundant. It has been found also in 
Brazil and Ceylon. Platinum melts at 1460° C. Platinum pos- 
sesses qualities which render it an extremely useful metal, but the 
sparseness of its distribution in nature, together with the difficulty 
of working, renders its cost so high as to prohibit its use in all but 
exceptional instances. 



RUTHENIUM. 99 



Platinum appears to be the only metal which is able to resist the 
chemical action which takes place at the positive electrode in the 
processes for electric bleaching. 

The stills or retorts used in concentrating sulphuric acid are of 
platinum. Vessels made of this metal are of the greatest use to 
the chemical analyst, since it resists the action of nearly all chemi- 
cals as well as great heat. 



PALLADIUM. 

Symbol, Pd. — Atomic weight, 106.5. — Specific gravity, 11.8. 

Palladium was discovered by Wollastoii in 1803. It occasionally 
occurs native, but usually forms one-half to one per cent, of the 
platinum ores. It is a white, lustrous metal, similar to platinum, 
but much harder. It melts at 1360° C. It is dissolved readily by 
nitric acid and aqua regia. Palladium has the curious property of 
absorbing hydrogen equal to 982 times its own volume, forming 
apparently an alloy with it. Mercury also, under certain circum- 
stances, alloys with hydrogen to form hydrogen amalgam. These 
reactions seem to indicate that hydrogen is in reality a metal. 
Palladium occurs only in very small quantities, and as yet no con- 
siderable economic use has been found for it. 



RHODIUM. 

Symbol, Eli. — Atomic weight, 104.3. — Specific gravity, 12.1. 

This is a rare metal, of no industrial importance, found alloyed 
with platinum in its ores, usually to the extent of about one-half 
of one per cent. 

RUTHENIUM. 

Symbol, Eu. — Atomic weight, 104.2. — Specific gravity, 11.4. 

A very rare metal discovered in 1845. Never native, but always 
alloyed with other of the platinum metals. Of no industrial im- 
portance. 



100 GENERAL CHEMISTRY. 

OSMIUM. 

Symbol, Os. — Atomic weight, 199. — Specific gravity, 22.48. 

A rare metal, also of the platinum family, discovered, in 1803. 
It is a bluish white, very infusible metal. It takes its name from 
the Greek word 007^7, meaning smell, on account of the pungent, 
irritating odor of its oxide, Os0 4 , whose vapor is extremely irritat- 
ing and poisonous. Osmium is the heaviest substance known. 

IRIDIUM. 

Symbol, Ir. — Atomic weight, 198. — Specific gravity, 21.15. 

Iridium was discovered in 1803. It sometimes occurs native, 
but usually as an alloy with osmium. It is a very hard, white, 
brittle metal. It is frequently used for making the points of gold 
pens. It is very rare, and of scarcely any importance in the arts. 
It takes its name from the Latin word iris, the rainbow, from the 
rapid changes of color due to different stages of oxidation which 
occur when the metal is heated. 



Part II. 
THE CHEMISTRY OF PAPER-MAKING. 



Part II. 
THE CHEMISTRY OF PAPER-MAKING. 

CHAPTER I. 

CELLULOSE (C 6 H 10 O 5 ). 

The physical features of the ordinary forms of cellulose are 
familiar to every paper-maker, since it forms the basis of all that 
he produces. It is essentially vegetable in its origin, and forms 
so large and important a part of the structure of all plants that 
it has been said that in the vegetable world the formation of cellu- 
lose may be considered as synonymous with growth. Cellulose 
also occurs to a limited extent in the animal kingdom, and has 
been found in the brain, in diseased human spleen, the skin of 
silkworms and of serpents, and in the mantles of certain molluscs. 

Cotton-wool, filter paper, and, in general, any vegetable fibre 
which has undergone the usual chemical processes of paper-making 
consist mainly of cellulose, with which are associated various 
other substances in greater or less amount. Pure cellulose is 
most readily obtained by treating cotton-wool or white filter paper 
with a boiling one per cent, solution of caustic soda, then with 
cold dilute hydrochloric acid, and after that with ammonia. The 
fibre should be carefully washed with water after treatment with 
each of these reagents, and finally exhausted with alcohol and 
ether. Thus obtained, cellulose is a white, translucent body, of 
Sp. Gr. about 1.45, and which preserves the form and general 
character of the fibres from which it was prepared. It resists the 
action of chemical reagents to a remarkable degree, as is shown 
by its wide use in the laboratory in the form of filter paper. 
Cellulose has, however, a powerful attraction for certain salts in 
solution, and water containing them may be so filtered through 

103 



104 THE CHEMISTRY OF PAPER-MAKING. 

a mass of cellulose as to have the dissolved salts completely 
removed. This attractive power is so strong in the case of vana- 
dium compounds that cellulose will separate them from solutions 
containing only one part of the salt in a trillion. 

Solutions of iron and alumina salts in contact with a quantity 
of pulp may have a considerable portion of the base fixed upon 
the fibre. Where iron is present, the color may thus be seriously 
affected. The process of mordanting cotton goods depends upon 
this affinity of cellulose for metallic bases. 

The formula for cellulose, C 6 H 10 O 5 , does not indicate the pres- 
ence of any mineral constituents, but even its most carefully puri- 
fied forms leave an appreciable amount of ash. In cotton this is 
usually from 0.1 to 0.2 per cent., though Herzberg gives a figure 
as high as 0.41 per cent., and bleached filter paper which has been 
washed with both hydrochloric and hydrofluoric acids leaves suffi- 
cient ash to render a correction for its presence necessary in very 
careful chemical work. 

The various reactions of cellulose prove it to be closely related 
to the sugars, starch, dextrin, glucose, and other members of that 
group of bodies which, including cellulose, are termed carbohy- 
drates. The formula of cellulose is the same as that of starch, 
and, like starch, cellulose can be readily converted into dextrin 
and glucose. (See, also, Celiulosic fermentation, p. 116.) 

The only known liquid in which cellulose dissolves without 
undergoing chemical change is Schweitzer's reagent, as it is called, 
though it is stated (Life of John Mercer, London, 1886) that 
its action was first studied by Mercer. This reagent may be pre- 
pared in various ways. Our own experience has led us to prefer 
the following method : cupric hydrate is precipitated by adding a 
solution of caustic soda to a cold solution of copper sulphate until 
nearly all the copper is precipitated. The hydrate is then carefully 
washed, and may be preserved under water in a glass-stoppered 
bottle. As the reagent is needed for use, it is made by dissolving 
the hydrate in ammonia of Sp. Gr. 0.900, until a saturated solution 
is obtained. When treated with Schweitzer's reagent, cellulose at 
first swells up and becomes gelatinous, but finally dissolves com- 
pletely to a thick syrupy solution. Erdmann and other chemists 
have contended that no true solution is formed, but recent experi- 
ments by Cramer on the osmotic properties of the solution prove 
that the cellulose is really dissolved. From this solution it may 



CELLULOSE. 105 



be precipitated in gelatinous nocks by the addition of acids, many 
salts, and, it is generally said, by simply diluting it largely with 
water and allowing the solution to stand in a closed vessel for eight 
to ten days. We think it doubtful if complete precipitation is ob- 
tained in this way, and we have allowed such dilute solutions, 
containing less than 0.25 gram of cellulose per litre, to stand in 
glass-stoppered jars for more than a month without causing any 
precipitation. The precipitate, as usually formed, contains, in 
addition to cellulose, considerable copper hydrate, which gives it 
a blue color, and which may be removed by washing with water, 
dilute acid, and then with water again. When a solution of lead 
acetate is used to precipitate the cellulose, the precipitate contains 
both cellulose and lead oxide in varying proportions ; while by 
digesting the same solution with finely divided lead oxide a defi- 
nite compound of cellulose and lead oxide (C e H 10 O 5 , PbO) is 
obtained. Metallic zinc, added to the solution of cellulose in 
Schweitzer's reagent, throws down the copper, which is replaced 
by zinc, forming a colorless solution similar in its properties to 
the original one. 

A practical application of the action of Schweitzer's reagent 
upon cellulose has been made on the large scale in the manufac- 
ture of the so-called Willesden papers and products. The reagent 
is prepared in quantity in a series of towers, loosely packed with 
copper scrap, over which strong ammonia is allowed to trickle, 
while air is drawn up through the towers. When a web of paper 
is passed through this solution, the fibres become superficially 
softened, and may be pressed into a continuous mass, or several 
sheets may be pressed together. No attempt is made to wash out 
the solution, which dries to a green varnish, coating the fibres, and 
rendering them waterproof and very durable. Canvas and rope 
cordage are similarly treated. 

A solution of iodine, prepared by dissolving one gram of iodine 
and five grams of iodide of potash in 100 c.c. of water, stains cellu- 
lose blue under certain conditions, and is used for its recognition 
under the microscope. If Iceland moss or some of the lichens and 
algse containing cellulose in its less compact forms are merely 
boiled with water, the cellulose is disintegrated, and the blue color 
is obtained on adding the above solution of iodine. With a fresh 
solution, cellulose in its denser forms, as in cotton and other puri- 
fied fibres, merely develops a yellow color, which may shade into 



106 THE CHEMISTRY OF PAPER-MAKING. 

brown; but if the fibres are first treated with sulphuric or phos- 
phoric acid, or zinc chloride, they are then stained blue with 
iodine. It would seem, therefore, that although this blue colora- 
tion is generally spoken of as characteristic of cellulose, it really 
depends not upon cellulose, but upon other bodies, whose presence 
is the result of the treatment to which the cellulose has been sub- 
jected. Schultze's solution of iodine gives a blue with cellulose 
at once, and may be prepared hy dissolving zinc in hydrochloric 
acid so long as there is any action, evaporating the resulting solu- 
tion of zinc chloride to a syrup, saturating with potassium iodide, 
and then adding enough iodine to color the whole brown. It may 
be used of various degrees of strength, but it is to be observed 
that the zinc chloride would exert a powerful action upon the 
cellulose, so that in this case also the blue coloration is probably 
due to modifications of the cellulose rather than to that substance 
itself and iodine. 

Concentrated sulphuric acid, Sp. Gr. 1.60, dissolves pure and 
thoroughly dry cellulose, a syrupy and almost colorless solution 
being obtained, which, on dilution with water and boiling, is con- 
verted into dextrin and glucose. If the boiling is continued for a 
long time, about five hours, only glucose, or similar reducing 
sugars, is obtained. As the glucose can be readily fermented, 
with consequent production of alcohol, it is thus possible to make 
both glucose and alcohol from such materials as sawdust and rags. 
Starch, under the same conditions, acts similarly and gives the 
same products. With more concentrated acid, especially if it be 
hot or if the cellulose is damp, there is a breaking down of the 
cellulose molecule, and, at the same time, more or less decompo- 
sition of the acid. Gases are evolved, in which carbonic and 
sulphurous acids may be recognized, and the liquid becomes black 
from the separation of carbonaceous matters. These are precipi- 
tated on pouring the acid into a considerable volume of water, 
and may be easily removed by filtration, leaving a golden colored 
liquid, whose color darkens when the acid is neutralized with 
ammonia. When treated with acid of the strength previously 
given, Sp. Gr. 1.60, or even with somewhat weaker acid, the 
cellulose first becomes gelatinous and more transparent. If the 
mixture is poured into water before the solution is complete, 
white flocks resembling hydrate of alumina are obtained, which 
dry to a horny mass. The substance composing them differs little 



CELLULOSE. 107 



from cellulose in composition, and is termed amyloid, from its 
resemblance to starch. Its composition is given as C^H^On. It 
is difficult to determine just when the cellulose is entirely dis- 
solved, owing to its transparency, and it is usually stated that pre- 
cipitation of amyloid occurs at once on diluting the clear solution. 
We find in our own experiments, using various strengths of acid, 
that when a clear solution is obtained there is no precipitation of 
amyloid upon dilution until a considerable time has expired, when 
at best only a small proportion of the cellulose is recovered in that 
form. The loss is probably due to the formation of dextrin. 
Amyloid forms the outer coating of the parchment paper which 
is largely used in dialyzing apparatus and for many of the purposes 
to which animal parchment was applied. 

Parchment paper is prepared by dipping unsized paper for a few 
seconds into sulphuric acid diluted with one-quarter to one-half or 
more its bulk of water, to which glycerine is sometimes added. 
After removing the paper it is washed with water, then with dilute 
ammonia or other alkali, and finally with pure water again. On 
the large scale the paper is treated in the web in a continuous way, 
passing into the acid, as into a vat for glue sizing, then between 
rollers, or " doctors," to remove the excess of acid, and from there 
into the dilute ammonia and water. Thus treated, the paper ac- 
quires a remarkable toughness and many of the properties of 
animal parchment. It undergoes a considerable linear shrinkage 
during the treatment (20 per cent.), and suffers some loss of 
weight (Cross and Bevan). The action of a concentrated solution 
of zinc chloride, about 65° Be. upon cellulose is similar to that of 
sulphuric acid. The so-called vulcanized fibre is formed of sheets 
of paper which have been treated Avith zinc chloride, then pressed 
together, and washed for a long time in running water to remove 
the chemical. 

The formation of parchment paper by means of sulphuric acid 
was first noticed by Poumarede and Figuier in 1847, from whom 
it received the name Papyrin. No practical application of their 
discovery was made until it was extended and patented by Gaines 
in 1857. 

The process has quite recently received an ingenious application, 
which would seem to make any alteration in the denomination of 
a bank note or other paper money impossible. The denomina- 
tion is printed in large numbers in the centre of the bill, the 



108 THE CHEMISTRY OF PAPER-MAKING. 

numbers being preceded and followed by a star or other device, 
thus — 

-4.10004*- 

Strong sulphuric acid or a solution of chloride of zinc is used in 
place of ink, and transforms the paper, which is generally tinted, 
into transparent vegetable parchment at the points where it is 
deposited, so that after washing and drying the numbers seem 
to be formed by a tough transparent membrane inserted in a 
colored sheet. The effect is highly artistic, and as the fibrous 
structure of the paper is destroyed at the points where the chemi- 
cals were deposited, it is practically impossible to alter the char- 
acters. 

When cellulose is heated in a sealed tube to 180°, with six to 
eight times its weight of acetic anhydride, it dissolves to a thick 
syrup. On pouring this into water white flocks of triaceto- 
cellulose are precipitated, which have the composition represented 
by the formula — 

C 6 H 7 (C 2 H 3 0) ; A. 

The compound dissolves in strong acetic acid, but is insoluble in 
water, alcohol, and ether. Alkalis easily remove the acid with 
recovery of the cellulose. This reaction is similar to the one tak- 
ing place when oils are treated with alkali, when glycerine is set 
free, and soap formed, and it therefore indicates that cellulose, like 
glycerine, may be considered a triatomic alcohol. This view is 
confirmed by the fact that it has been found impossible to prepare 
compounds containing more acetic anhydride than the above, no 
matter how great an excess of the anhydride is used or how long 
the heating is continued. It is to be noted also, in this connection, 
that by the action of nitric acid upon cellulose nitro-substitution 
products are formed similar in many of their properties to the 
nitroglycerines. 

The action of nitric acid upon cellulose was first studied by 
Pelouze, who observed in 1838 that it resulted in the conversion 
of the cellulose into an explosive substance. Schonbein, in 1846, 
announced the discovery of an explosive cotton, but kept its 
method of preparation secret. It was independently discovered 
soon after by Bottger and Otto, by the latter of whom the method 
was published. Several disastrous explosions of large quantities 
of the material as at first made caused it to be considered utterly 



CELLULOSE. 109 



unlit for use, until von Lenk and Abel pointed out the precautions 
necessary to secure the production of a material of constant com- 
position, and which remained perfectly stable under all ordinary 
conditions. Knop had previously shown that a mixture of nitric 
and sulphuric acids gave better results than nitric acid alone, and 
the explosive called guncotton is now prepared as follows : Loosely 
spun yarn or cotton wool is first purified by boiling in a dilute 
solution of carbonate of potas*h to remove resinous, gummy, and 
waxy matters or oil. It is then carefully washed with water and 
dried, after which it is placed in a mixture of one part of nitric 
acid, Sp. Gr. 1.5, and three parts sulphuric acid, Sp. Gr. 1.85, and 
allowed to remain twenty-four hours. Great pains are taken to 
keep the mixture cool. The nitrated cotton, after washing, is 
removed to a beating-engine, where it is washed again and reduced 
to pulp. It is then ready to be pressed into hexagonal blocks or 
into cylinders. 

The composition of guncotton was determined by Crum, who 
gave it the formula — 

C 12 H 14 (X0 3 ) 6 4 , 

or that of a hex-nitrate of cellulose. Guncotton is also called 
Pyroxylin, though this term is usually extended to comprise the 
other nitrates of cellulose as well. Its general appearance is the 
same as that of the cotton from which it was prepared, but it is 
harsher to the touch, and its fibres, viewed under the microscope 
by polarized light, do not show the brightness and play of color 
exhibited by ordinary cotton. It becomes strongly electrical on 
being rubbed, crackling and emitting sparks, and is phosphorescent 
in the dark (Gaiffe). It is slowly soluble in acetone, but insoluble 
in water, methyl alcohol, glacial acetic acid, Schweitzer's reagent, 
alcohol, or ether, or in mixtures of the last two liquids. Weak 
acids and alkalis do not affect it. Strong sulphuric acid dissolves 
it slowly, and upon heating the solution carbonic acid and nitric 
oxide are given off, though there is no blackening. It dissolves 
rapidly in strong potash lye when heated to 70°, with formation of 
ammonia, nitrous acid, oxalic acid, and other bodies of acid char- 
acter. The alkaline solution precipitates silver from an ammonia- 
cal solution of the metal, and the reaction has been utilized in a 
process for silvering mirrors. Alkaline solutions of moderate 
strength remove more or less nitric acid from guncotton on warm- 
ing, the proportion of acid removed varying with the strength of 



110 THE CHEMISTRY OF PAPER-MAKING. 

the solution (Eder). A solution of potassium sulphydrate in 
dilute alcohol converts the nitrate into the original cotton, potas- 
sium nitrate and some ammonia being formed. Ferrous sulphate 
and ferrous acetate or a solution of stannous oxide in caustic soda 
have the same effect. In contact with sulphuric acid and mercury, 
guncotton gives up its nitrogen as nitric oxide. These reactions, 
like that with acetic anlrydride, indicate that cellulose is analogous, 
in many of its chemical relations, to* the alcohols. 

Concentrated sulphuric acid displaces the nitric acid in gun- 
cotton even in the cold. A method of estimating the nitrogen in 
pyroxylins is based upon the fact that when they are boiled with 
ferrous sulphate and hydrochloric acid the nitrogen is set free as 
nitric oxide (Eder). 

Besides guncotton, which contains six N 3 , there have been pre- 
pared several other lower nitrates of cellulose, containing succes- 
sively five, four, three, and two N0 3 . They differ from guncotton 
mainly in being less explosive, and in the fact that they are 
soluble in a mixture of alcohol and ether. The penta-nitrate, 
C 12 H 15 5 (N0 3 ) 5 , is best prepared, according to Eder, by dissolving 
guncotton in hot nitric acid, about 90° C, then cooling to 0°, when 
it is precipitated as the penta-nitrate on addition of sulphuric acid. 
The precipitate is washed with a large amount of water, and fur- 
ther purified by being dissolved in a mixture of alcohol and ether, 
from which the pure nitrate is thrown down on addition of water. 
By the action of strong solutions of potash upon the penta-nitrate 
a portion of the acid is removed, leaving di-nitrate of cellulose. 

The extent to which the nitration of the cellulose is carried 
when in contact with the mixed acids depends upon the strength 
of the acids employed and upon the time for which it is exposed to 
their influence. Thus, by shortening the time of immersion to a 
few minutes, or by the use of weaker acids, a mixture of the tetra- 
nitrate, C 12 H 16 6 (N0 3 ) 4 , and tri-nitrate, C 12 H 17 7 (N0 3 ) 3 , is obtained. 
These are readily soluble in a mixture of alcohol and ether, in 
acetic ether, and in methyl alcohol. The solution in ether-alcohol 
mixture is called collodion, and the tetra- and tri-nitrates are 
termed collodion pyroxylins. 

The di-nitrate, C 12 IT 18 8 (N0 3 ) 2 , is the result of the action of a 
hot dilute mixture of nitric and sulphuric acids upon cellulose. 
It dissolves in the solvents mentioned in the preceding paragraph. 
All of the higher nitrates are finally reduced to this body when 



CELLULOSE. Ill 



treated with alkaline solutions ; but if the action is carried too far, 
there is a further decomposition with production of a brown 
gummy mass. The mono-nitrate has not been formed. 

Celluloid and zylonite are prepared by treating the lower 
nitrates, collodion pyroxylins, with camphor, either melted or as 
spirits of camphor. This reduces the pyroxylin when hot to a 
plastic condition, in which it can be readily worked and moulded 
into a great variety of articles, and which permits the incorpora- 
tion of coloring matters and other substances. 

Celluloid in the mass burns about as readily as paper, and with 
a smoky flame. It cannot be exploded by any ordinary means. 
The camphor present may be removed by ether. Thin, trans- 
parent plates and rolls of celluloid are now much used in photog- 
raphy, as their flexibility and lightness give them great advantage 
over glass. In this form celluloid flashes up quickly and burns 
without smoke. 

Collodion — the solution of pyroxylin in ether-alcohol mixture 
— rapidly dries on exposure to the air, and forms a tough, lustrous 
varnish. It is largely used in surgery as a covering for wounds, 
in photography as a vehicle for the silver salts, and in the match 
manufacture for rendering the tips of matches waterproof. Pure 
sulphite fibre or unsized paper made therefrom is sometimes used 
instead of cotton in the preparation . of both celluloid and col- 
lodion. 

The nitrates of cellulose and their reactions have received a new 
interest for the paper-maker through their recent application in the 
process of manufacturing artificial silk. This product, which re- 
sembles silk only in its physical properties, was first 
shown at the Paris Exposition of 1889, where it at- 
tracted much attention. It is prepared by the follow- 
ing process of M. de Chardonnet : — 

Cotton or pure chemical fibre is nitrated and dis- 
solved in a mixture of thirty-eight parts ether to forty- 
two parts alcohol to form collodion. This is placed 
in a copper vessel, and forced by air pressure through 
capillary glass tubes into water. In Fig. 2, A shows 
the glass tube through which the collodion passes. 
B is a second tube surrounding the first, and supplied 
with water through the inlet C. The collodion solidifies upon 
contact with the water, forming a smooth thread, which is carried 




112 THE CHEMISTRY OF PAPER-MAKING. 

forward by suitable mechanical arrangements through a drying 
chamber to the bobbins. J. H. du Vivier, Br. Pat. 2570, A. d. 1889, 
prepares three solutions as follows : — 

1. A 12.5 per cent, solution of gutta percha in carbon bisulphide. 

2. A 5 per cent, solution of isinglass in glacial acetic acid. 

3. A 7 per cent, solution of pyroxylin in glacial acetic acid. 

These are mixed in such proportion that the resulting solution 

contains — 

4 parts nitrocellulose, 

1 part isinglass, 



part gutta percha, 



to which is added a little castor oil and glycerine. The thread 
coming from the capillary aperture is led first through a bath of 
soda, then into one containing albumen, and finally into a solution 
of bichloride of mercury to coagulate the albumen. It then passes 
through the vapor of carbon bisulphide on its way to the bobbins, 
and may be treated with ammonia and alum in order to sufficiently 
impregnate it with alumina to prevent its burning readily. The 
combustible nature of the nitrocellulose renders the soda or other 
chemical bath necessary, as the nitric acid is thereby removed in 
greater part. Chardonnet employs a bath of nitric acid of Sp. Gr. 
1.32, the temperature of which is slowly allowed to fall from 35° to 
25°, by which means, it is stated, the fibre is denitrated and reduced 
to the condition of ordinary cellulose. 

This new fibre promises to have an important, bearing on the 
textile industries, as it compares favorably with silk as to strength, 
while surpassing silk in lustre and beauty. It may be dyed 
brilliantly in any color. 

Cellulose and Chlorine. — Dry chlorine has no effect upon 
cellulose, but when moisture is also present, as when the gas is 
passed into water containing cellulose in suspension, the cellulose 
is rapidly oxidized and carbonic acid evolved. A similar action is 
observed when cellulose is heated with a solution of bleaching 
powder or other hypochlorite. Cross and Bevan have lately shown 
that in ordinary bleaching there is often some chlorination of the 
cellulose. The extent of the chlorination appears to depend some- 
what upon the base present, and is stated by them to be conspicu- 
ously less when hypochlorite of magnesium is used instead of 
bleaching powder. We find, in electric bleaching, that fibre 
caught and held against the positive electrodes where it is sub- 



CELLULOSE. 113 



ject to the action of nascent chlorine is after some weeks con- 
verted into a yellow, gummy substance, all fibrous structure being- 
lost. By acting upon guncotton in a sealed tube with phosphorous 
penta-chloride Baeyer has indirectly prepared a compound of cellu- 
lose and chlorine, which was obtained as a viscous liquid which 
mixed readily with alcohol and ether. 

Cellulose and Oxygen ; Oxycellulose. — The action of oxidiz- 
ing agents upon cellulose has been studied by Witz, who finds that 
their first effect is to convert the cellulose more or less completely 
into a white, friable substance, containing less carbon and more 
oxygen than cellulose, and for which he has proposed the name 
oxycellulose. The frequent tendering of cotton cloth in bleaching, 
or in boiling with milk of lime, is due to partial conversion into 
oxycellulose. When cotton or linen cloth is wet with a solution 
of bleaching powder, and exposed for some time to the air, there is 
a gradual loss of strength and change of composition as indicated 
above. Kept in a very slightly acidulated solution of bleaching 
powder for several days, the fibre is so completely changed to 
oxycellulose that it readily rubs down to a white powder. When 
converted into oxycellulose, no reducing agent, as antichlor, will 
restore the fibre to its original condition. 

Oxycellulose has a powerful attraction for basic aniline dyes, 
though not for those of acid character, and the greater readiness 
with which fibre may be colored after bleaching is due in part to 
the superficial formation of this substance. Many aniline blacks 
are dyed upon cloth which has been partially converted into oxy- 
cellulose and which are consequently lacking in strength. 

Vanadium salts are often used in the preparation of fast aniline 
blacks, and oxycellulose has the remarkable property of forming 
compounds with vanadium even in solutions containing only one 
part of the element in 1,000,000,000,000. By converting portions 
of a fabric into oxycellulose by the action of oxidizing agents, the 
cloth may be dyed topically by dipping in a basic dye. 

Fehling's solution is reduced by oxycellulose, which is colored 
red by the precipitated copper oxide. We have noticed the for- 
mation of oxycellulose in parchment paper held in the wooden 
frames of clialyzing apparatus used for glue solutions, the change 
seeming to have been induced by contact with the slowly decay- 
ing wood. Upon boiling such paper with Fehling's solution the 
copper oxide was deposited in streaks, coinciding with the position 



HI THE CHEMISTRY OF PAPER-MAKING. 

of the softer portions of the grain of the wood. The paper was 
unaffected where it had not touched the wood. 

Through the action of more powerful oxidizing agents than 
those which bring about the formation of oxycellulose, cellulose is 
split up into a number of simpler molecules. Treatment with 
strong permanganate or bichromate of potash gives glucose, dextrin, 
and formic acid among the decomposition products. Hot chromic 
acid burns cellulose in the wet way, carbonic oxide and carbonic 
acid being formed. Upon this reaction Cross and Bevan have based 
a method of ultimate analysis. Certain metallic oxides, notably 
iron rust, in contact with moist cellulose, convert it into glucose 
and a gummy substance which changes to glucose on boiling with 
dilute acid. 

Hydrocellulose. — When cellulose is moistened with any dilute 
mineral acid and then driecl, or when it is exposed for some time 
to their vapor, it »is changed to a friable substance having the 
composition C 12 H 22 O n , and named by Girard, hydrocellulose; by 
Witz, hydracellulose. Girard has shown that the modification 
thus brought about in cellulose is one of true hydration, since 
pure cotton treated for five days with pure dry hydrochloric acid 
gas showed no trace of change, while it was rapidly converted to 
hydrocellulose in the presence of moisture and the acid. Liquid 
organic acids also modify cellulose considerably, but not to so great 
an extent as do mineral acids. Hydrocellulose is soluble in warm 
potash lye. It absorbs oxygen when heated, even at so low a 
temperature as 50°, and after being kept for some hours at 80° to 
100° in contact with the air is converted into dark ulmic com- 
pounds, which are soluble in water. Hydrocellulose does not, like 
oxycellulose, attract basic aniline dyes, but both these substances, 
like cellulose, form explosive nitrates when treated with the 
mixed acids. 

In the process of removing burrs from wool, and cotton fibre 
from mixed goods, the materials are moistened with dilute sul- 
phuric acid and dried, by which treatment the cellulose is con- 
verted into hydrocellulose, which from its brittle nature may be 
separated by mechanical means. It is sometimes dissolved out by 
weak alkali, the wool in either case being unaffected. A strong 
solution of aluminum chloride has recently been used to replace 
the dilute acid in the " carbonizing " process. 



CELLULOSE. 115 



Water at High Temperatures. — The effect of heat upon 
cellulose is greatly increased by the presence of water, the cellu- 
lose being partially decomposed with formation of carbonic acid 
and dark brown products of acid character. Mulder was the first 
to observe the formation of a small quantity of glucose at the 
same time. By extracting pure filter paper, under pressure in a 
Miincke's digester, Tauss obtained yellow extracts passing into 
brown on exposure to the air, and depositing on evaporation a 
black resinous precipitate, soluble in alkalis. Three hours' treat- 
ment at 75 pounds pressure gave an extract containing, per 100 
grams of cellulose, 1.385 grams total solids, of which 0.1285 
grams were glucose or similar reducing sugars. Cellulose, under 
about 300 pounds pressure, was completely changed to a jelly-like 
mass, which could be powdered after drying. Its composition was 
then the same as that of hydrocellulose, C 12 H 22 0ii. 

The manufacture of chemical fibre by the soda process proves 
that the action of hot and moderately strong solutions of the 
alkalis has, at most, only a superficial action upon cellulose. 
Concentrated solutions, Sp.'Gr. about 1.3, cause cellulose to swell 
up and become transparent in much the same way that it does in 
the preparation of parchment paper. Cloth thus treated and 
washed free from alkali is said to be Mercerized, from Mercer, who 
first prepared it. The cloth shrinks considerably in the operation, 
but acquires additional strength. The mercerized cellulose also 
shows a greater tendency than before to absorb water. Gladstone, 
using soda-lye of Sp. Gr. 1.342, has noted the formation of a com- 
pound of soda and cellulose, C^H^Oio + NaOH, which is resolved 
by carbonic acid or even by washing with water. When equal 
parts of potassium hydrate and cellulose are moistened with water 
and heated in a closed vessel, hydrogen, methyl alcohol, and wood- 
spirit are driven off, while carbonic, formic, and acetic acids are 
found in combination with the potash. Heated in contact with the 
air the main product is oxalic acid. 

Cellulose is decomposed by various fermentative processes, 
especially those going on in the digestive canal. It is dissolved 
with liberation of marsh gas, by the fluid from the vermiform 
appendix of the rabbit. In the rumen and large intestine of 
herbivora it is decomposed into fatty acids and gases, consisting 
mainly of carbonic acid and hydrogen. This has been shown in 
the laboratory by Tappeiner, who placed cotton-wool in flasks 



116 THE CHEMISTRY OF PAPER-MAKING. 

with Nageli's salt solution and asparagine. Upon addition of 
fluid from the rumen, fermentation set in, with evolution of volatile 
acids, hydrogen and carbonic acid. 

In nature, when the supply of air is somewhat limited and 
moisture is present, cellulose gradually decays with formation of 
large quantities of marsh gas and the dark brown or black amor- 
phous substances which constitute vegetable mould or humus. 
This consists mainly of acid products, soluble in alkaline solutions. 
Among them have been recognized ulmin and ulmic acid, humin 
and humic acid. This decomposition has an important bearing 
on the character of the soil, not only through the mechanical 
action of the evolved gases in loosening the soil, but by the power 
possessed by humus of fixing atmospheric nitrogen in a form suit- 
able for plant life (Storer). 

A peculiar fermentation, called Cellulosic fermentation, which 
Durin first observed in beet juice possesses much interest in con- 
nection with the study of cellulose. It is there due to a ferment 
very similar to diastase, but may be induced in solutions of cane 
sugar through the influence of certain fatty seeds, as rape and colza. 
It results in the formation of hard, white, warty lumps, which ex- 
hibit all the reactions of cellulose, while from the mother-liquor 
there is precipitated, on the addition of alcohol, another body, 
similar to cellulose in composition, but tough and glutinous. Upon 
placing some of these lumps in a solution of cane sugar the forma- 
tion of cellulose continues at the expense of the sugar, the solution 
finally containing only a trace of that substance. It has been shown 
in case of many plants whose juices are rich in sugar, that as the 
cellulose increases, the sugar lessens in amount, and there is little 
doubt that in general cellulose is formed in the living plant from 
sugar and substances of similar composition in the sap. Such food 
as the plant stores or holds in reserve is elaborated in the form of 
starch, which may be then, possibly by the action of ferments, 
converted into sugar or its isomers, to be dissolved and carried by 
the sap. 



FIBRES. 117 



CHAPTER II. 

FIBRES. 

The Vegetable Cell. — The unit of structure in the plant is the 
vegetable cell. All living cells consist essentially of protoplasm, 
which in the higher plants is surrounded by a wall of cellulose, pro- 
duced by the protoplasm at the limiting film, and laid down in close 
contact with the him. The protoplasm is to be regarded as the 
actual basis of the life of the plant, as indeed it is the actual basis 
of all life. Chemically considered, it belongs to the group of 
albuminous bodies, and is closely similar in appearance and com- 
position to the albumen which forms the white of egg. Under the 
microscope the protoplasm is seen to maintain a constant circula- 
tion, which is rendered visible by the granules in its substance, 
and by means of which nutritive matters are brought from the out- 
side to the denser portion, called the nucleus, while the waste 
products are carried to the surface of the mass. 

The green color of plants is due to the presence at certain points 
of a peculiar coloring matter called chlorophyll, or, more properly, 
chlorophyll pigment, which is associated with certain of the denser 
or more differentiated portions of protoplasm, called chlorophyll 
granules. The coloring matter is developed only through the 
action of light. It is soluble in alcohol, the solution appearing 
green in transmitted and blood-red in reflected light. The chloro- 
phyll granules are the agents by which, under the influence of 
light, the plant decomposes the carbonic acid always present in the 
atmosphere, and assimilates the carbon needed for building up the 
plant-structure. 

It is only in very young cells that the cell-wall consists of pure 
cellulose, and even here it contains a trace of mineral matters. 
With increasing age various changes in the wall take place, either 
through degradation of the cellulose itself, or more generally by 
the infiltration of other substances upon it. Through the deposi- 
tion of silica upon or within the cell-wall the wall may be so 
hardened and stiffened that the change is called mineralization. 



118 THE CHEMISTRY OF PAPER-MAKING. 

Calcium salts are sometimes so deposited, and well-defined crystals 
of the oxalate or carbonate are not infrequently formed within the 
cell. 

Either with or without these mineral matters there is often a 
deposition upon the cell- wall of suberin, or cork substance. The 
cell thereby gains greatly in elasticity and such suberized cells are, 
as would be expected, much less permeable to water and gases than 
the normal cells. 

Lignin. — By far the most important change which, from our 
present point of view, occurs in the cell-wall is that known as 
lignification, and caused by the formation and infiltration upon 
the wall of a substance somewhat analogous to cellulose and 
called lignin. Lignin, which probably consists of several closely 
related substances, forms by far the greater portion of the incrust- 
ing matters which it is the object of several of the preparatory 
processes of paper-making to remove. These changes do not 
always extend throughout the cell-wall, but often only definite 
layers or strata of the wall are thus affected. The numerous 
researches of Cross and Bevan have led them to regard the lignified 
cell-wall as a chemical whole, from which by appropriate processes 
cellulose may be reduced. We are ourselves disposed to adhere 
to the older view, which considers the incrusting matter as some- 
thing laid down in intimate contact with the cellulose of the wall, 
which itself remains unchanged, and reappears when the incrusting 
matters are removed by solvents. Contrary to the statement of 
Erdmann, and in support of our belief, we find that Schweitzer's 
reagent readily removes the cellulose from lignified wood-cells. 
'The solution dissolves over 35 per cent, of beech, spruce, gumwood, 
and birch after they have been extracted with water, alcohol, and 
ether. After boiling the extracted and washed residue with dilute 
hydrochloric acid enough more of the wood is dissolved by the 
Schweitzer reagent to bring the total quantity removed to over 60 
per cent, of the dry wood. 

Compared with cellulose lignin is harder and more elastic and 
absorbs relatively little water. The hardness of wood is generally 
in proportion to the amount of lignin it contains. The acetic acid 
produced in the distillation of wood appears to be derived chiefly 
and the wood-spirit wholly from lignin. Alkaline solutions dis- 
solve lignin at a temperature of 130° C. with formation of acid 
products. Fused with caustic potash it is converted into ulmic 



FIBRES. 119 

acid. Treatment with oxidizing agents, as chlorine, bromine, 
chromic acid, permanganate of potash, or dilute nitric acid, con- 
verts lignin into resinous acids, soluble in dilute alkali, or the 
oxidation may even proceed to the formation of carbonic acid and 
water. 

A solution of aniline sulphate in water or alcohol stains lignin 
yellow ; nitric acid produces a yellowish brown coloration ; phloro- 
glucin gives a rose-red stain when the specimen has been previ- 
ously treated with hydrochloric acid; a solution of indol produces 
a similar effect upon lignified tissues which have first been moist- 
ened with dilute sulphuric acid, made by mixing one part of 
strong acid with four of water. All of these reagents are of much 
value for detecting the presence of incrusting matters in paper- 
making fibres, or in the finished product. Comparative tests may 
easily be arranged to show the thoroughness with which the boil- 
ing operation has been conducted in the manufacture of Avood 
fibre, the depth of color produced by the reagent being in a 
measure proportional to the amount of incrusting matter still 
remaining in the fibre. 

The chemical composition of lignin is still a matter of some 
doubt. It is known to contain more carbon than cellulose, 
and Fremy gives the formula C 18 H 20 O 8 , while Schuppe finds it to 
be C 19 H 18 O s . Although, as previously stated, lignin is probably 
made up of several analogous bodies, it may, for practical purposes, 
be regarded as a single substance, and will be so referred to by us. 
Payen distinguishes four different components, thus: — 

Lignose. — Insoluble in water, alcohol, ether, and ammonia; 
soluble in caustic soda and potash. 

Lignin. — Insoluble in water and ether ; soluble in alcohol, 
ammonia, caustic potash, and soda. 

Lignone. — Insoluble in water, alcohol, ether; soluble in am- 
monia, caustic potash, and soda. 

Lignireose. — Soluble in all the above reagents, but only slightly 
so in water. 

Their percentage composition, according to the same author, is 
as below : — 





Carbon. 


Hydrogen. 


Oxygen. 


Lignose . 


. 46.10 


6.09 


47.81 


Lignin 


. 62.25 


5.93 


81.82 


Lignone . 


. 50.10 


5.82 


44.08 


Lignireose . 


. 67.91 


6.89 


25.20 



120 THE CHEMISTRY OF PAPER-MAKING. 

The thickening of the cell-wall, which is the result of the deposi- 
tion of lignin upon the cellulose, and which, up to a certain point, 
accompanies increase of age, does not in most cases take place 
uniformly over the entire surface of the wall. As a consequence, 
depressions or markings, having in different instances the form of 
pits, lines, rings, or spirals, appear in the gradually thickening 
wall, and often become so distinct and characteristic as to afford 
one of the best means for the identification of the fibres in which 
they occur. Diffusion of sap and water or gases proceeds with 
greatest freedom at these thinnest portions of the wall. 

The formation of gums and resins, although not wholly under- 
stood, is doubtless due to changes of degradation in the cell-wall. 
The products may either be found as minute, irregularly shaped 
drops within the cell itself, or in the spaces formed by the break- 
ing down of several cells, or, as in the case of spruce and other 
coniferous trees, in distinct receptacles, known as resin-passages. 
The resins are soluble in alcohol and in alkaline solutions, and are 
stained yellow by tincture of alcannet root. They may be distin- 
guished under the microscope by their appearance and these 
reactions. 

Protoplasm is found only in the living cells, and these are at 
the points of growth. Where protoplasm is absent, growth has 
ceased, and such older lifeless cells generally contain only air more 
or less highly rarefied. In some cases they contain water or a 
few granules. Their usefulness to the plant has by no means 
ceased, however, for from them the plant-structure derives in the 
main its strength and stiffness. The different plant-cells present 
an almost infinite variety of form, but, except in case of those 
which serve as a means of identification for the fibres which they 
accompany, we shall endeavor to confine ourselves to those long- 
drawn, pointed elements of the bast and wood, which are properly 
called fibres, and which alone, with the single exception of cotton, 
possess a practical interest for the paper-maker. They are derived 
from the ordinary primitive cells by progressive growth and change 
of form. 

The fibres which are commonly used in paper-making may be 
divided, according to their relations to the plant from which they 
are derived, into four classes. 

1. Seed-hairs, as cotton, which is the only representative of the 
class. 



FIBRES. 121 

2. Bast-fibres, as linen, jute, manila, adansonia. 

3. Those derived from whole stems or leaves, and associated 
with various vessels and cells not properly fibres, as straw, esparto, 
sorghum, bamboo. 

4. Those derived from wood. 

1. Seed-Hairs. 

Cotton (Grossypium). — All of the many known varieties are 
derived from the three species, Gr. Barbadense, sea-island cotton, 
which has a very soft, silky staple nearly two inches in length ; 
Gr. herbaceum, upland or short staple cotton ; G. arboreum, which 
sometimes attains the height of a small tree. 

The cotton fibre consists of a single slender cell or hair, the 
hairs forming the covering of cotton seeds. The length of 
the fibre varies from 2-5 cm.; diameter, from 0.012-0.037 mm. 
The widest are found in upland cotton of short staple ; the aver- 
age for sea-island cotton is 0.023 mm. The ripe fibre presents the 
appearance of a collapsed tube spirally twisted ; the unripe cells 
show little or no twist. See Plate I. 24-29. Ordway mentions a 
single fibre which had a breaking weight of 149.4 grains. 

Schunck has found in raw cotton two coloring matters : (a) 
soluble in alcohol, insoluble in ether ; (5) insoluble in cold alcohol, 
soluble in boiling alcohol; both containing nitrogen. He has also 
found a wax similar to carnauba wax; pectic acid; albuminous 
matter, and a solid crystalline fatty acid. All of the above are 
soluble in solutions of the alkalis and alkaline carbonates. Miiller 
has analyzed the raw fibre with result as below : — 

Per cent. 

Water 7.00 

Cellulose 91.35 

Fat 0.40 

Aqueous extract (containing nitrogenous 

substances) 0.50 

Ash 0.12 

Cuticular substance (by difference) . . 0.63 

2. Bast-Fibres. 

The term bast was first applied to the inner bark of the bass- 
wood, and later was extended to include the inner bark of other 
plants. The long, tough cells found in such barks were called 



122 



THE CHEMISTRY OF PAPER-MAKING. 



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FIBRES. 123 

bast-libres. Similar cells occur, however, throughout other portions 
of many plants, and all such cells are now collectively termed 
bast-fibres or liber-fibres. By far the greater number of the fibres 
in use throughout the world belong to this class. 

The walls of bast-fibres are generally much thickened through 
lignification, and crystals are often present in the cavity. The 
thickening is often very uneven and may cause projections of the 
Avail, within the cell. There are also in the different fibres 
such considerable variations in the extent of lignification, and in 
the kind and quantity of foreign substances deposited on and in 
the wall, that the behavior of the fibres with reagents is often 
sufficiently characteristic to serve roughly for their identifica- 
tion. 

The length of the single fibres is seldom sufficiently great to 
permit their use in textile manufactures, and their peculiar value 
for such purposes lies in the fact that as they occur in the plant 
they are associated together to form bundles, which often attain 
great length. We shall reserve the name filaments for these bun- 
dles, to distinguish them from the ultimate fibres of which they 
are composed. The fibres are generally firmly attached to those 
immediately above and below them by partial identity of their 
Avails, or by incrusting matter, and in most cases a chemical treat- 
ment is necessary to effect their separation from each other. The 
separation of the filaments from the body of the plant is brought 
about in various ways, one of the most common being the well- 
known retting process applied to flax. 

See table on page 122. 

According to the report by Cross and Be van, on Indian fibres and 
fibrous substances exhibited at the Colonial and Indian Exhibition, 
London, 1886, to which Ave are indebted for much of our material 
relating to these fibres, there are in India over 300 fibre-bearing 
plants, of which 0A r er 100 yield strong and useful fibres, regularly 
employed by the natives of that country. As Ave shall give in 
many cases the results of the chemical examination of the fibres 
by these chemists, reference should be had to the subjoined scheme, 
on page 124, which was folloAved in their investigations: — 



124 THE CHEMISTRY OF PAPER-MAKING. 

Moisture. Hygroscopic water or water of condition. 

Separate Portion taken for each Determination Below. 
Results calculated in Percentage of Dry Substance. 

Ash Total residue left on ignition. 

Hydrolysis (a) . . . Loss of weight on boiling raw fibre five min- 
utes in one per cent, solution of caustic soda. 
" (&) . . . Loss of weight on continuing to boil one hour. 

Cellulose White or bleached residue from following 

treatment ■ (1) Boil in one per cent, caustic 
soda five minutes ; (2) exposure to chlorine 
gas one hour; (3) boil in basic sodium 
sulphite. 

Mercerizing .... Loss on treating one hour with 33 per cent. 

solution of caustic potash, cold. 

Nitration Weight of nitrated product obtained by treat- 
ment with mixture equal volumes nitric and 
sulphuric acids, one hour in the cold. 

Acid purification . . Raw fibre boiled one minute with acetic acid 

(20 per cent.), washed with water and 
alcohol, and dried. 

Carbon percentage . . The carbon in the fibre from above determined 

by combustion. 

Linen (fibres of flax plant) (Jjinum usitatissimum). — The 
plant yields 7.9 per cent, of fibre, which is separated by a fer- 
mentative process termed retting, and is then called flax. The 
fibres (Plate I, 51-56) are thick-walled tubes, showing knots or 
septa at intervals, and often creases. The internal cavity is of 
very small relative diameter. Filaments run entire length of stem. 
Bleached with more difficulty than cotton. Miiller gives the fol- 
lowing analyses of two samples of heckled Belgian flax: — 

Cellulose 81.99 70.55 

Fat and wax 2.37 2.34 

Aqueous extract 3.62 5.94 

Pectous substances .... 2.72 9.29 

Water 8.60 10.56 

Ash . .70 1.32 

The figures obtained by Cross and Be van on a sample of heckled 
Irish flax are as follows : — 



FIBRES. 125 



Moisture 9.1 

Following percentages are on dry basis. 

Ash 1.6 

Hydrolysis (a) ........... 13.3 

" (b) 22.1 

Cellulose ............ 80.2 

Mercerizing 8.4 

Nitration 125.0 

Acid purification 4.3 

Carbon percentage . 43.2 

As they occur in bleached linen cloth the fibres are nearly pure 
cellulose. 

Jute (Corchorus capsularis and C. olitorius). — Filaments 
obtained by retting and maceration of stem. Jute butts and cut- 
tings are the stumps. Much of the fibre received by paper-makers 
in the form of gunny bags. 

The fibres (Plate I, 7-10) are primarily bound together, forming 
filaments containing 6-20 fibres. As ordinarily used in paper- 
making, with only partial bleaching, the fibres are not completely 
separated, and the resulting stock is therefore especially long and 
strong. Fibres are thick-walled, highly lignified, contain much 
coloring matter ; section is polygonal. 

Jute, as the type of lignified fibres, has been carefully studied by 
Cross and Bevan, who regard it as a chemical whole, termed by them 
ligno-cellulose, which splits up into cellulose, as one product, upon 
treatment with appropriate reagents. They find evidences of ligni- 
fication in even the youngest fibres. The fibre is easily chlorinated 
by the moist gas or chlorine water, and then becomes bright yellow, 
which changes to magenta in solution of sodium sulphite. 

Composition of raw fibre (Miiller) : — 

First Quality. Cuttings or Butts. 

Cellulose 63.76 60.89 

Fat and wax 0.38 0.44 

Aqueous extract .... 1.00 3.89 

Non-cellulose or lignin . . 24.32 20.98 

Water 9.86 12.40 

Ash . . 0.68 1.40 



126 THE CHEMISTRY OF PAPER-MAKING. 

From a sample of unusually good quality Cross and Bevan ob- 
tained figures as below : — 

Moisture 10.3 

Following percentages are on dry basis. 

Ash 1.2 

Hydrolysis (a) 15.0 

(6) 18.0 

Cellulose 75.0 

Mercerizing 16.0 

Nitration 125.0 

Acid purification 1.0 

Carbon percentage 46.5 

Hemp (Cminahis sativa). — Filaments run entire length of 
stem, separated from bark by process of retting. Fibres (Plate I, 
57-62) much resemble linen ; fine hairs, however, project from the 
septa or knots. Walls very thick, not highly lignified. 

Composition of raw Italian hemp (Miiller) : — 

Cellulose . . 77.13 

Fat and wax 0.55 

Aqueous extract 3.45 

Pectous substances 9.25 

Water 8.80 

Ash 0.82 

Many other plants yield fibres to which the name hemp is 
applied, but they are usually distinguished as sunn hemp, manila 
hemp, etc. 

Manila — Manila hemp — (Musa textiles') . — Filaments separated 
by the natives in the Philippine Islands by drying and scraping 
the outer sheath (leaf petioles) of the stem of the plant, which 
is a species of banana; further purified by beating and washing. 
Each tree produces only about one pound of fibre. 

Ultimate fibres much shorter than in hemp ; cavity much more 
conspicuous; number of fibres in section of filament much greater; 
section of fibre more or less polygonal. 



FIBRES. 127 

Composition of raw fibre (Miiller) : — 

Cellulose 64.07 

Fat and wax . 0.62 

Aqueous extract 0.96 

Lignin and pectous substances .... 21.60 

Water 11.73 

Ash 1.02 

Figures obtained by Cross and Be van: — 

Moisture 10.5 per cent. 

Following percentages are on dry basis. 

Hydrolysis (6) 13.5 per cent. 

Cellulose 58.0 " 

Sunn Hemp (^Crotalaria juncea). — Filaments, which contain 
20-50 fibres, separated from stem by retting as with jute. Fibres 
3-5 mm. long, polygonal, cavity small, show spiral markings. 
With iodine and sulphuric acid fibre is colored a mixed blue and 
brown; shows yellow stains or streaks with sulphate of aniline. 
Sunn is not a true hemp, but is derived from a plant of the pea 
family. 

Composition of raw fibre (Miiller) : — 

Cellulose 80.01 

Fat and wax 0.55 

Aqueous extract 2.82 

Pectous substances 6.41 

Water 9.60 

Ash 0.61 

New Zealand Flax (Pliormmm tenax) . — Name flax mislead- 
ing ; filaments are separated from the leaves, which, when air-dry, 
yield 49.5 per cent of cellulose (Cross), and which attain a length 
of 1-2 metres. Fibres nearly white, soft, lustrous, not highly ligni- 
fied ; walls not so thick as in true flax ; smooth ; no knots ; cavity 
much larger than in flax (linen). 

Percentage of cellulose in the raw fibre variously given from 
67 to 86.3, the higher figure being more probably correct. 

Ramie QBoehmeria tenacissima). — Fibres stiff; lustrous like 
silk ; take brilliant colors ; sometimes single ; average in filament 
three ; section ovoid to polygonal ; cavity large. Separated with 
some difficulty from plant. After separation bleach easily. 

Percentage of cellulose 75 (Cross). 



128 THE CHEMISTRY OF PAPER-MAKING. 

China Grass — Rhea — (Boehmeria nivea). — Not a grass, but like 
ramie a shrubby plant, the filaments being derived from the inner 
bark. General characteristics of ultimate fibres similar to those of 
ramie, but in this species the maximum length is much greater. 
This is the longest fibre (ultimate cell) known, the length reaching 
220 mm. (8.66 inches) in some cases. The stiffness of the fibre is 
its great drawback. 

Coir — Cocoanut fibre — (Cocos nucifera). — Filaments sepa- 
rated from the husk of the cocoanut by soaking for months in water 
and then carding. Has been pulped by Ekman in one hour, by boil- 
ing under pressure with bisulphite of magnesia. Mainly used for 
mats, probably never in practice as paper-stock. Mixed with clay 
it has been used as an exterior coating for sulphite digesters. 

Adansonia (inner bark of baobab or monkey-bread tree) (Adan- 
sonia digitata). — Has attracted some notice from English paper- 
makers. Makes a strong paper which takes a high finish. The 
composition of the bast as exported varies, as shown below : — 

Cellulose ....... 49.35 58.82 

Fat and wax ...... 0.94 0.41 

Aqueous extract 13.57 7.08 

Pectous substances .... 19.05 15.19 

Water 10.90 13.18 

Ash 6.19 4.72 

Paper Mulberry Tree {Broussonetia papyrifera). — The fibres 
of the inner bark are used by the Japanese in making their peculiar 
paper. Fibres are separated by scraping, soaking, and maceration 
in water ; are bleached in the sun, and sometimes further purified 
by boiling in weak lye. The bark yields a glutinous substance 
which acts as a size. 

The fibres are 6-20 mm. long, soft, lustrous. According to 
Vetillart, they appear under the microscope nearly transparent ; 
have longitudinal marks or strise, and are often flattened on each 
other and convoluted like a ribbon ; the points are fringed and 
terminate in a round end. They have a tendency to curl up into 
rings. 

As they occur in Japanese paper the fibres are usually unbroken. 

The bark yields 62.5 per cent, of unbleached or 58 per cent, of 
bleached fibre (Routledge). 



FIBRES. 129 

Agave — Aloe — Century plant — (Agave Americana). , — Fila- 
ments separated from leaves, by maceration or scraping ; large, 
white, lustrous, stiff ; fibres 2-6 mm. in length (Cross and Bevan), 
or 1.02-2.2 mm. (Goodale) ; walls thick ; cavity conspicuous ; sec- 
tion polygonal ; ends either tapering or forked. 

Sisal hemp or heniquen is derived from Agave ixtli, common in 
Yucatan and Mexico. About one and a quarter pounds of fibre 
are produced yearly by each plant. Largely used for cordage, 
bags, etc., and comes in these forms to the paper-mill. 

Cross gives the following figures on Agave keratta from the 
West Indies : — 

Moisture „ 15.5 

Following percentages are on dry basis. 

Ash 1.4 

Hydrolysis (a) 10.0 

(6) 20.0 

Cellulose 75.8 

Mercerizing 11.0 

Nitration 109.8 

Acid purification 0.4 

Length of ultimate fibres 2-8 mm. 

3, Fibres derived from whole stems and associated in the pulp ivith 
cells and vessels not properly fibres. 

The fibres in this class, although bast or libriform fibres, are 
separated by treating the whole stem by a chemical process. The 
resulting pulp consists of the ultimate fibres, — the filaments being 
broken up in the process of treatment, — and cells from the epi- 
dermis and other portions of the plant. 

Straw (the stems and leaves of the various cereals). — Straw 
pulp consists of the ultimate bast fibres and accompanying cells, 
freed from the incrusting and other matters by a chemical proc- 
ess. The bast cells or fibres form the greater portion of the pulp. 
They are comparatively short and fine ; at nearly regular intervals 
the wall appears somewhat thicker than elsewhere, and drawn 
together (Plate I. 30, 31). The fibres and the accompanying 
cells are stained blue by iodine solution, but these thickened por- 



130 



THE CHEMISTRY OF PAPER-MAKING. 



tions show a reddish brown coloration. The dimensions of the 
fibres from different straws are given below : — 





Length. 


Width. 


Wheat . 


. . 0.152-0.449 mm. 


0.018-0.024 mm 


Rye . . 


. 0.086-0.345 "' 


0.012-0.016 " 


Barley . 


. 0.103-0.224 " 


0.012-0.014 " 


Oats . . 


. . 0.186-0.448 " 


0.012-0.017 " 



The most characteristic feature of straw pulp is the occurrence 
of epidermal cells (Plate I. 37, 39, 41) with serrated or toothed 
edges. These cells show great differences in size, and the propor- 
tion of length to width varies from 1 : 1 to 10 : 1. The differences 
are sufficiently marked and constant to enable the different varieties 
of straw to be distinguished in the pulp. Associated with the 
epidermal cells are others from the pith (Plate I. 35, 36), which 
aid in the recognition of this pulp. These cells vary in shape 
from the nearly round to an oval or much more elongated form. 
The width is usually great in comparison to the length. Portions 
of vessels and other elements occasionally occur (Plate I. 32, 33, 
34, 40). 

ANALYSES OF STRAW (WOLFF & KNOP). 





Winter 
wheat. 


Winter 
rye. 


Winter 
barley. 


Oats. 


Water 


14.3 

5.5 
2.0 


14.3 
3.2 
1.5 


14.3 
5.5 
2.0 


14.3 


Ash 


5.0 




2.5 


Carbohydrates, etc 


30.2 


27.0 


29.8 


38.2 




48.0 


54.0 


48.4 


40.0 




1.5 


1.3 


1.4 


2.0 



The percentage of pure cellulose in dry straw is given by Cross 
and Bevan as below : — 

Oat straw 52.0 

" " 53.5 

Wheat 49.6 

Eye 53.0 

Arendt has exhaustively investigated the composition of different 
parts of the oat plant at different periods of growth. The straw 



FIB BE S. 131 

contains 30-40 per cent, of water when fully ripe, much more if 
cut earlier. Straw is of best quality if cut before ripening is com- 
pleted. When about a foot (0.31 m.) high both stem and leaves 
contain about 23 per cent, of crude fibre on the dry substance ; at 
commencement of ripening the stem contains 36-41, and the leaves 
29-33 per cent, of fibre, the proportion being in each case lowest 
in the upper part of the plant. 

Straw yields a white wax soluble in alcohol and solutions of 
caustic alkali. The amount of ash, which is often more than half 
silica, ranges from about 3-7, or in exceptional cases as" high as 
12 per cent, on the dry straAv. The strongest straw yields the 
most ash. 

Esparto — Alfa — Spanish Grass. — The rush-like leaves of 
Stipa tenaeissima and Lygeum spartnm, which grow wild in Spain 
and Northern Africa. Spanish esparto is considered the best. 

The bast fibres occur in bundles or filaments, which are resolved 
into ultimate fibres by the method of treatment. Fibres (Plate I. 
43, 49) similar to those of straw, but shorter, more even, and with 
cavity nearly closed. Serrated cells (Plate I. 47, 48) common, but 
smaller than those of straw. Esparto pulp is distinguished from 
straw pulp by the presence of small, tear-shaped cells (Plate I. 
45 Z) and the absence of the oval cells. 

Miiller gives the composition of esparto as below : — 

Spanish. African. 

Cellulose 48.25 45.80 

Fat and wax 2.07 2.62 

Aqueous extract 10.19 9.81 

Pectous substances .... 26.39 29.30 

Water 9.38 8.80 

Ash 3.72 3.67 

The analyses of Cross and Bevan give : — 

Cellulose, 
per cent, on dry basis. 

Spanish . 58.0 

Tripoli 46.3 

Arzew 52.0 

Oran 49.6 

In paper esparto fibre is tougher than straw. The yield of air- 
dry fibre on the dry plant is from 45-55 per cent. 



132 THE CHEMISTRY OF PAPER-MAKING. 



Bamboo (Bambusa). — About 170 species are described by 
Munro, Bambusa vulgaris being the one most generally distributed. 
Mr. Thomas Routledge, who first worked esparto in England, pub- 
lished in 1875 a pamphlet, calling attention to the value of bamboo 
as a source of paper-stock, and printed upon an excellent paper 
made from that material. Microscopical examination of this 
paper shows the pulp to possess the general characteristics of that 
from straw. The bast fibres are short, fine, with thick walls ; 
serrated cells numerous and of various shapes and sizes ; numerous 
ovoid cells from the pith, some nearly square, all pitted. Cells 
similar to those found in esparto (Plate I. 45) and to those shown 
in Plate I. 33, 34, were also noticed. The proportion of these 
different cells to the fibre present is very large, and from their 
small size many must be lost in working the pulp. 

The bamboo has been known to attain a height of forty feet in 
forty days, and Routledge estimates the yield per acre at forty tons 
of green stems, or six tons of paper-stock per annum. When the 
stems are cut before maturity, they are easily reduced b}^ crushing 
and boiling with caustic soda. 

Bagasse and Sorghum. — The crushed stalks and diffusion 
chips of the sugar cane and sorghum have been often proposed 
and occasionally used as a raw material for paper-making. They 
are easily reduced by boiling with weak soda, and the resulting 
pulp is much like that from straw. On account of the large pro- 
portion of pith the yield of fibre is only about 25 per cent, on the 
dry stalk, and the samples which we have seen were so badly 
specked by fragments of seed hulls as to be useless for making any 
but the cheapest papers. 

4. Wood. 

The cells or elements which make up the woody tissue of plants 
exhibit great diversity of form and markings, as is shown in Figs. 3 
and 4 taken from Sanio. Those which especially deserve consid- 
eration as furnishing a raw material for paper-making are the trite 
wood fibres and the tracheitis. Many of the other cells are, how- 
ever, of interest, as they serve in some cases to identify the wood 
from which they were derived. The wood fibres or libriform cells 
never show true spiral markings, and the pits, which rarely occur 
in the cell-wall, are not especially noticeable. In certain of them, 



FIBRES. 



133 



called septate cells, the cavity instead of being continuous through- 
out the whole length of the cell, as in most cases, is divided into 
two or more compartments by partitions perpendicular to the 
long-er axis. The lenerth of the wood fibres and the extent to 
which their cell-wall is thickened by lignification show great 
variations in different plants. Some of the longest have a length 
of 2.0 mm., while others are as short as 0.14 mm. Their arrange- 




Wood Elements from Various Plants. 



ment in the plant stem also varies in different cases, being some- 
times radial, and in other instances showing an irregular grouping. 
Chemical pulp made from poplar consists almost entirely of true 
wood fibres. 

For the practical purposes of paper-making trachei'ds are to be 
regarded as fibres, since they possess the same elongated shape 
and tapering ends. They are, however, to be distinguished from 



134 



THE CHEMISTRY OF PAPER-MAKING. 



the libriform fibres by the numerous large and well-defined mark- 
ings, which from their shape are called bordered pits or discoid 
markings. These markings arise with the gradual thickening of 
the cell-wall until finally they assume the appearance shown in 
Figs. 5, 6, and 7. 

The wood of cone-bearing or coniferous trees, like spruce, fir, and 
hemlock, consists entirely of trache'ids, and the discoid markings 




4. [M 
■1 \\ 


MIH 


37 


1 



Fig. 4. — Wood Elements from Various Plants. 

are very apparent when sulphite pulp, made from these woods, 
is examined under the microscope. They are even more readily 
seen in ground wood. These trache'ids are much longer than 
the libriform fibres occurring in the wood of other trees, but in 
the common case, in which both trache'ids and fibres occur in 
the same wood, the fibres are always the longest elements in the 
particular wood considered. 



FIBRES. 



135 



Growth of Wood. — Growth in the widest sense takes place by 
the division of cells. A single cell is converted into two by the 
formation of an excessively thin membrane of cellulose. This 






Fig. 5. 

Bordered pits or discoid markings of the wood cells (trache'ids) of Pinus laricio : 
a, aspect, of radial walls; b, a transverse section; c, development of the markings 
in Pinus sylvestris (Sanio). 



single membrane is at first a common wall for the two adjacent 
cells, but as growth proceeds and the thickness of the membrane 
increases it commonly splits into two adjacent walls. The growth 
of wood depends upon the activity 
of a thin layer of tissue lying im- 
mediately under the bark, and 
called the cambium layer. The 
cells composing this layer are filled 
with protoplasm, and by their sub- 
division and growth new wood is 
formed upon the old wood in con- 
centric rings or layers. As growth 
altogether ceases during winter, 
and as the character of the wood 
produced varies periodically at dif- 
ferent seasons of the year, these 
rings become visible, and serve as a register of the annual growths. 
The fibres and trache'ids formed during the spring have compara- 




Fig. 6. 



Pinus sylvestris. Transverse sections 
of perfect and nearly perfect discoid 
markings (Strasburger) . 



136 



THE CHEMISTBY OF PAPER-MAKING. 




Fig. 7. 



Portion of wood-cell 
showing bordered pits 
of radial wall ; b, section through 
wall (Herzberg). 



(trache'id) 
a, aspect 



tively thin walls, and are somewhat larger than those formed 
during the autumn. 

Autumnal wood is somewhat more 
dense and contains more incrustinp; 
matter than spring wood. A section 
through the wood shows that the au- 
tumnal fibres are considerably flattened 
by the pressure of the bark, which is 
greatest at this time, while the section 
of the fibres formed in the spring is 
nearly square, as shown in Fig. 8. 

Sap and Heart Wood. — The wood 
of comparatively recent growth, or sap- 
wood, often called from its color albur- 
num, contains a larger proportion of 
sap and putrescible matters than the 
older and harder heart-wood or dura- 
men, so called on account of this 
greater hardness and durability. The 
difference in color and hardness is not 
always evident, as, for example, in the 
fir and sweet buckeye. Each year a ring 
of sap-wood passes over into the con- 
dition of heart-wood, and then takes no 
further part in the activity of the plant. 
It becomes darker by the infiltration of 
coloring-matter. The thickness of the sap- 
wood is practically constant, while that of 
the heart-wood increases with each succeed- 
ing year. Heart wood is for most pur- 
poses of much greater value than sap-wood, 
and when ground into pulp should be less 
likely to deteriorate with age than pulp 
made from sap-wood. There is, however, 
a prejudice among pulp-makers in favor of 
sap-wood, or for the younger trees in which 
it is present in greatest amount, and it is 
quite probable that such wood, because of 

its smaller content of lignin, would be less brittle under grinding, 
and would therefore yield a longer fibre. 




Fig. 8. 



FIBRES. 137 

The cells in the earliest annual rings are considerably smaller 
than those in the succeeding rings, and the increase in size pro- 
ceeds regularly until after a number of years a maximum is 
reached and maintained in the rings formed afterward. 

This fact is brought out in the following table by Sanio, quoted by 
Goodale, based on measurements of trache'ids of Pinus sylvestris : — 

Number of the annual Medium length of Medium width of 

ring. the trache'ids. the trache'ids. 

1 0.95 mm. 0.017 mm. 

17 2.74 " 

19 3.13 " 

31 3.69 " 

37 3.87 " 

38 3.91 " 

39 4.00 " 

40 4.04 « 

43 4.09 c < 

45 4.21 " 

46 4.21 " 

72 4.21 " 0.032 mm. 

All wood contains in the cell cavities a large amount of air and 
water, the former being highly rarefied. According to Sachs, 
100 c.c. of freshly cut fir consists of 

Mass of cell-walls 24.81 c.c. 

Water 58.63 " 

Air cavities 16.56 " 

A determination by ourselves of the amount of water in green 
spruce as received at the mill gave 37 per cent, by weight. It is 
much larger in growing or freshly cut wood. 

Gelesnoff determined the water in entire trees each month for a 
year. Scotch pine gave a maximum (January) of 64.0 per cent., and 
a minimum (May) of 55.3 per cent. ; average for the year 61.1 per 
cent. Aspen gave a maximum (March) of 56.6 per cent., and a 
minimum (May) of 48.9 per cent.; average for the year 52.8 per 
cent. Birch gave a maximum (May) of 65.9 per cent., and a mini- 
mum (December) of 43.5 per cent. ; average for the year 49.2. 

The hardness and density of wood is largely dependent upon 
the amount of lignin which it contains. The lignin not only 
tends to harden the cell-walls, but also by its presence lessens the 
space within the cells which might otherwise contain air. The 



138 



THE CHEMISTRY OF PAPER-MAKING. 



following table, compiled from the reports of the Tenth United 
States Census, gives the density, ash, and fuel value of the woods 
commonly used for pulp-making. The determinations were made 
by Mr. S. P. Sharpies, under direction of Professor Sargeant: — 



Botanical Name. 


Common Name. 


Specific 
gravity. 


Weight of 
cubic foot 
in pounds. 


Ash, 
per 
cent. 


Heat units evolved 
by combustion 
of one kilo- 
gramme of dry 
wood. 


Pinus Strobus. 


White pine. 


0.3485 


21.72 


0.12 


4272.69 


Pinus Banksiana. 


Gray pine of 












Canada. 


0.4761 


29.67 


0.23 


— 


Picea nigra. 


Spruce. 


0.4087 


25.47 


0.30 


3949.37 


Abies grandis. 


Fir. 


0.3545 


21.97 


0.49 


— 


Abies Fraseri. 


Balsam. 


0.3565 


22.22 


0.54 


— . 


Larix Americana. 


Tamarack. 


0.7024 


43.77 


0.27 


4182.04 


Populus granclidentata. 


Poplar. 


0.4632 


28.87 


0.45 


— 


Populus tremuloides. 


Aspen. 


0.3785 


23.59 


0.74 


4292.31 


Populus monilifera. 


Cottonwood. 


0.4494 


28.00 


0.65 


4242.15 


Salix nigra. 


Willow. 


0.4456 


27.77 


0.70 


— 


Fagus ferruginea. 


Beech. 


0.7175 


44.71 


0.54 


3895.04 


Acer dasycarpum. 


Maple. 


0.5269 


32.84 


0.33 


— 


Betula alba. 


White birch. 


0.6160 


38.05 


0.29 


4073.05 


Betula papyrifera. 


Paper birch. 


0.6297 


39.24 


0.23 


4101.41 


iEsculus glabra. 


Buckeye. 


0.4542 


28.31 


0.86 


— 


Liquidambar styraciflua. 


Sweet gum. 


0.5615 


34.99 


0.48 


4016.46 


Taxodium distichum. 


Cypress. 


0.4084 


24.45 


0.40 


4739.73 


Tsuga Canadensis. 


Hemlock. 


0.4097 


25.53 


0.48 


4208.58 


Castanea vulgaris. 


Chestnut. 


0.4621 


28.80 


0.13 


4092.96 


Tilia Americana. 


Basswood. 


0.4525 


28.20 


0.55 


— 


Robinia pseudacacia. 


Locust. 


0.7257 


45.22 


0.23 


3890.02 



The heaviest wood found in the United States is black iron-wood, 
Condalia ferrea, which has a specific gravity of 1.3020, and is also 
remarkable for its large amount of ash, 8.31 per cent. The lightest 
is Ficus aurea, which has no common name. Its specific gravity is 
0.2616, and ash 5.03 per cent. Both trees are found in Florida. 

Resins. — Although, as previously pointed out, the formation of 
resins is not fully understood, they are known to be immediately 
derived from the oxidation of essential oils which, occur in the 
tree. If the resins contain gum or mucilage, they are termed gum- 
resins, while if they are mixed with the essential oils, .they are 
variously called oleo-resins, turpentines, or balsams. The term 
oleo-resin is the more comprehensive one, and only such oleo- 



FIBRES. 



139 



resins as contain benzoic or cinnamic acid are, properly speaking, 
balsams. The well-known but misnamed Canada balsam is a true 
turpentine. The oleo-resins are generally viscous liquids, like 
honey, but sometimes occur as soft solids. 

The resins are insoluble in water, difficultly soluble in hot bisul- 
phite solutions, readily soluble in alcohol and alkaline solutions. 
They are to be regarded as mixtures of several analogous bodies, 
and various substances of acid character are recognized among their 
components. Sylvic acid, with others, is found in common rosin. 
Rosin, often called colophony, is the residue left on distilling off the 
volatile oil (spirits of turpentine) from the turpentine obtained 
from Southern pine. The color of rosin ranges from light yellow to 
dark red, the darker color being, at least in part, a result of the 
increased temperature to which the rosin was exposed in order to 
drive off all the spirits of turpentine. The specific gravity of rosin 
is usually about 1.083, but the ver}?- light-colored varieties may 
have a specific gravity of only 1.040, while that of the darkest 
specimens may run as high as 1.100. One hundred parts of refined 
rosin will completely neutralize about eighteen parts of caustic 
potash, KOH. According to Sargeant, the fuel value of resinous 
woods is about 12 per cent, higher than that of those containing 
little or no resin, but the statement is evidently a general one. 

The quality of a wood for pulping, especially by the acid proc- 
esses, depends largely upon its freedom from any excessive quan- 
tity of resin, and nearly as much upon the evenness with which 
the resin is distributed. If the resin is mainly localized at certain 
points or rings, the other portions of the wood may be reduced 
with comparative ease, while the more resinous portions still 
remain hard, and largely increase the proportion of chips and shive 
in the pulp. Ulbricht has studied the distribution of resin in the 
spruce fir, Abies excelsa, with the result shown below. He includes 
as resin all matter soluble in alcohol and not in water. 

PARTS OF RESIN PER 100 OF WOOD. 





Sap-wood. 


Heart- wood. 


Entire wood. 


Spring 


1.966 
1.781 
1.987 
2.024 


2.299 
2.041 
2.235 
2.158 


2.213 
1.911 


Summer 


2.109 


Autumn 


. 2.137 







140 



THE CHEMISTRY OF PAPER-MAKING. 



We have made determinations of the quantities of material 
removed from the following woods by water, and by a successive 
treatment with ether and alcohol, with results as shown. The 
figures give per cents, on the dry basis : — 





Water — removes 
gums, mucilage, 
sugars, tannin, etc. 


Ether. 


Alcohol. 


Total removed by 
ether and alcohol 
— includes resins, 
oils, waxes, etc. 


Spruce 


4.83 


1.G7 


1.61 


3.28 


Poplar 


4.80 


0.85 


1.00 


1.85 


Cottonwood . . . 


4.69 


0.79 


2.04 


2.83 


Sweet gum . . . 


3.39 


0.30 


0.55 


0.85 


Beech 


2.14 


0.38 


0.55 


0.93 


Yellow birch . . . 


1.88 


0.32 


0.65 


0.97 


Cypress .... 


4.22 


0.81 


0.94 


1.75 



The analyses of a number of European woods has been carried 
much farther by Miiller, and from his results we select those of 
especial interest. 

PROXIMATE ANALYSES OF WOODS. 
Hugo Mullee {Die Pflanzenfaser) . 





Water. 


Soluble in 
water. 


Soluble In 

alcohol and 

benzine. 


Cellulose. 


Incrusting 
matter. 


Incrusting 
matter for 
every 100 
of cellulose. 


Black poplar 
Silver fir 

Willow . . 
Scotch pine 
Chestnut 

Beech . 
Ebony . 








12.10 
13.87 
12.48 
11.66 
12.87 
12.03 
10.10 
12.57 
9.40 


2.88 
1.26 
2.65 
2.65 
4.05 
5.41 
3.56 
2.41 
9.99 


1.37 
0.97 
1.14 
1.23 
1.63 
1.10 
3.93 
0.41 
2.54 


62.77 
56.99 
55.52 
55.72 
53.27 
52.64 
53.09 
45.47 
29.99 


20.88 
26.91 
28.21 
28.74 
28.18 
28.82 
29.32 
39.14 
48.08 


33.3 
47.2 
50.8 
51.6 
52.9 
54.7 
55.2 
86.1 
160.3 



Bark and Knots. — Simultaneously with the production of a 
layer of wood, through the activity of the layer of cambium tissue 
surrounding it, there is formed on the outside of this tissue a layer 



FIBRES. 141 

of bark, which serves as a protective envelope to the stem. Cork 
cells, or those upon whose walls has been deposited suberin or 
cork substance, are admirably fitted on account of their imper- 
meability to protect the underlying tissues and occur, often in 
layers, in the bark. Associated with them, more especially in the 
inner bark, are the long bast fibres which give strength to the 
bark. As the bark increases in thickness, the outer layers become 
more or less completely cut off" from the underlying tissue by 
layers of cork cells, and, as a result, this outer portion dries up and 
dies, becoming sometimes deeply fissured as the trunk expands 
with growth. The bark is often rich in tannin and coloring mat- 
ters; that of hemlock containing 13-16 percent, of tannin; and, 
on account of the permanence of these colors and the slight extent 
to which suberin is affected by reagents, the bark is only slightty 
acted upon by the chemical processes for pulping wood ; indeed, 
in the sulphite process hardly at all, and, if present with the chips, 
remains to form black or brown specks in the pulp. 

An experiment to determine the shrinkage of pulp wood in 
barking gave result as follows : one cord of green spruce, containing 
37 per cent, moisture, and cut in four-foot lengths, weighed 4440 
pounds ; after barking the weight was 3570 pounds. 

Knots are formed at the point where a branch makes out from 
the stem, and consist of the dead and dried tissue, usually very 
dense and highly charged with coloring matters. They are partially 
reduced by the soda process, but entirely resist the action of the 
reagents employed in the sulphite process, which usually fails even 
to soften them appreciably. 

The woods most commonly employed in the United States for 
the manufacture of ground wood and chemical fibre are spruce 
and poplar. A number of other woods are used, however, in con- 
siderable, though varying, amounts, as the factors of price, length 
of fibre, ease of reduction, and relation of the mill to the source of 
supply may determine in particular cases. We shall consider 
briefly these different woods, with reference to their occurrence, 
general features, and availability for pulp-making. Their specific 
.gravity, ash, and fuel value have already been given. The state- 
ments regarding the occurrence and general character of the several 
woods are taken from the exhaustive Report on Forest Trees, by 
Professor Sargeant, in the reports of the Tenth United States 
Census. The scientific names by which the different species are 



142 



THE CHEMISTRY OF PAPER-MAKING. 



designated by different authors show a lack of uniformity almost 
as great as that which prevails in common usage regarding the 
common names. We have therefore followed the nomenclature 
of the report to which we have just referred. The species given 
by no means comprise all those which are or may be used, but are 
to be considered as typical of the different sorts of wood employed. 
Thirty-five species of pine {Pinus) are enumerated in the report 
quoted as found in the United States. 

Black Spruce (Picea nigra). — Newfoundland, northern Lab- 
rador to Ungava Bay, Nastapokee Sound, Cape Churchill, Hudson 
Bay, and northwest to the mouth of the Mackenzie River and the 
eastern slope of the Rocky Mountains; south through the northern 
states to Pennsylvania, central Michigan, Wisconsin, and Minne- 
sota, and along the Alleghany Mountains to the high peaks of 
North Carolina. 

Wood light, soft, not strong, close, straight grained, compact, 
satiny; bands of small summer cells thin, resinous, resin passages 
few, minute ; medullary rays few, conspicuous ; color, light red or 
often nearly white, the sap-wood lighter. 

Easily reduced to a strong, long-fibred pulp by the sulphite proc- 
ess ; with somewhat more difficulty by the soda process ; pulp 
made by the latter process bleached with difficulty. We have 
made the following analyses of different samples of the ground 
wood : — 





A. 


B. 


c. 


Moisture 


11.31 

0.32 

52.96 

35.41 


11.48 

0.25 

53.08 

35.19 


11.26 


Ash 


0.30 


Cellulose 


52.98 


Lignin, etc., by difference 


35.46 




100.00 


100.00 


100.00 



Gray Pine (Pinus Banksiana). — Bay of Chaleur, New Bruns- 
wick, to the southern shores of Hudson Bay, northwest to the 
Great Bear Lake, the valley of the Mackenzie River, and the east- 
ern slope of the Rocky Mountains between the fifty-second and 
sixty-fifth degrees of north latitude ; south to northern Maine, 
Ferrisburg, Vermont (R. E. Robinson), the southern shore of 
Lake Michigan, and central Minnesota. 



FIBRES. 143 

Wood light, soft, not strong, rather close grained, compact; 
bands of small summer cells not broad, very resinous, conspicuous, 
resin passages few, not large ; medullary rays numerous, obscure ; 
color, clear light brown or, rarely, orange, the thick sap-wood 
almost white. 

Reduced to pulp with somewhat more difficulty than spruce ; 
fibres long as in spruce. 

W,hite Pine — Weymouth pine — (Pinus strobus). — Newfound- 
land, northern shores of the Gulf of Saint Lawrence to Lake 
Nipigon and the valley of the Winnipeg River, south through the 
northern states to Pennsylvania, the southern shores of Lake 
Michigan, "Starving Rock," near La Salle, Illinois, near Daven- 
port, Iowa (Parry), and along the Alleghany Mountains to north- 
ern Georgia. 

Wood light, soft, not strong, very close, straight grained, com- 
pact, easily worked, susceptible of a beautiful polish ; bands of 
small summer cells thin, not conspicuous, resin passages small, not 
numerous nor conspicuous ; medullary rays numerous, thin ; color, 
light brown, often slightly tinged with red, the sap-wood nearly 
white. 

Requires more severe treatment than spruce, but yields very 
long, strong fibre. 

White Fir (Abies grandis). — Vancouver Island, south to 
Mendocino County, California, near the coast; interior valleys of 
western Washington Territory and Oregon south to the Umpqua 
River, Cascade Mountains below 4000 feet elevation, through the 
Blue Mountains of Oregon (Cusick) to the eastern slope of the 
Cceur d'Alene Mountains (Cooper), the Bitter Root Mountains, 
Idaho (Watson), and the western slopes of the Rocky Mountains 
of northern Montana (Flathead region, Canby & Sargeant). 

Wood very light, soft, not strong, coarse grained, compact; 
bands of small summer cells broader than in other American 
species, dark colored, resinous, conspicuous; medullary rays nu- 
merous, obscure ; color, light brown, the sap-wood rather lighter. 

Requires somewhat more severe treatment than spruce, but 
yields very long, strong fibre. 

Balsam QAbies Fraseri). — High mountains of North Carolina 
and Tennessee. 

Wood very light, soft, not strong, coarse grained, compact; 
bands of small summer cells rather broad, light colored, not con- 



144 THE CHEMISTRY OF PAPER-MAKING. 

spicuous ; medullary rays numerous, thin ; color, light brown, the 
sap-wood lighter, nearly white. 

Occasionally reduced by the sulphite process ; unbleached fibre 
carries considerable pitchy material, which is likely to cause 
trouble in mill, and which interferes with bleaching. General 
character of fibre similar to spruce. 

For the purposes of his process Mitscherlich considers balsam 
and spruce identical. 

Hemlock (Tmga Canadensis) . — -Nova Scotia, southern New 
Brunswick, valley of the Saint Lawrence River to the shores of 
Lake Temiscaming, and southwest to the western borders of north- 
ern Wisconsin ; south through the northern states to New Castle 
County, Delaware, southeastern Michigan, central Wisconsin, and 
along the Alleghany Mountains to Clear Creek Falls, Winston 
County, Alabama (Mohr). 

Wood light, soft, not strong, brittle, coarse, crooked grained, 
difficult to work, liable to wind-shake, and splinter, not durable ; 
bands of small summer cells rather broad, conspicuous; medullary 
rays numerous, thin ; color, light brown tinged with red, or often 
nearly white, the sap-wood somewhat darker. 

General character of pulp similar to spruce, but wood is reduced 
with more difficulty, and is likely to cause chips if mixed with 
spruce. 

Larch — Tamarack — Hackmatack — (Larix Americana'). ■ — 
Northern Newfoundland and Labrador to the eastern shores of 
Hudson Bay; Cape Churchill, and northwest to the northern 
shores of the Great Bear Lake and the valley of the Mackenzie 
River within the Arctic Circle; south through the northern states 
to northern Pennsylvania, northern Indiana and Illinois, and cen- 
tral Minnesota. 

Wood heavy, hard, very strong, rather coarse grained, compact, 
durable in contact with the soil ; bands of small summer cells 
broad, very resinous, dark colored, conspicuous ; resin passages 
few, obscure ; medullary rays numerous, hardly distinguishable ; 
color, light brown, the sap-wood nearly white. 

Reduced by sulphite process with some difficulty; fibre some- 
what sticky from pitchy material, and requires a large amount of 
bleach. Wood if mixed with spruce is likely to cause chips. 
Length of fibre comparable to spruce. 

Poplar QPopnlus grandidentata~). — Nova Scotia, New Bruns- 



FIBRES. 145 



wick, and west through Ontario to northern Minnesota; south 
through the northern states and along the Alleghany Mountains 
to North Carolina, extending west to middle Kentucky and 
Tennessee. 

Wood light, soft, not strong, close grained, compact ; medullary 
rays thin, obscure ; color, light brown, the sap-wood nearly white. 

The wood most commonly used by mills working the soda proc- 
ess ; never used by sulphite mills, though easily reduced by 
that process. Pulp from both processes very easily bleached. 
Fibre short and soft, associated in the pulp with much wider 
pitted cells (Plate I. 19). 

Aspeu (Populus tremuloides). — Northern Newfoundland and 
Labrador to the southern shores of Hudson Bay, northwest to the 
Great Bear Lake, the mouth of the Mackenzie River, and the val- 
ley of the Yukon River, Alaska ; south in the Atlantic region to 
the mountains of Pennsylvania, the valley of the lower Wabash 
River, and northern Kentuck} r ; in the Pacific region south to the 
valley of the Sacramento River, California, and along the Rocky 
Mountains and interior ranges to southern New Mexico, Arizona, 
and central Nevada. 

Wood light, soft, not strong, close grained, compact, not durable, 
containing, as does that of the whole genus, numerous minute, 
scattered open ducts ; medullary rays very thin, hardly distinguish- 
able ; color, light brown, the thick sap-wood nearly white. 

Much resembles poplar in character of pulp and ease with which 
wood yields to treatment. 

Cottonwood. (Populus monilifera). — Shores of Lake Cham- 
plain, Vermont, south through western New England to Chatta- 
hoochee region of western Florida, west along the northern shores 
of Lake Ontario to the eastern base of the ranges of the Rocky 
Mountains of Montana, Colorado, and New Mexico. 

Wood very light, soft, not strong, close grained, compact, liable 
to warp in drying, difficult to season ; medullary rays numerous, 
obscure; color, dark brown, the thick sap-wood nearly white. 

Much resembles poplar in character of pulp and ease with which 
the wood yields to treatment. 

Sweet Gum (Liquidambar styraciflua). — Fairfield County, 
Connecticut, to the valleys of the lower Ohio, White, and Wabash 
Rivers, south to Cape Canaveral and Tampa Bay, Florida, south- 
west through southern Missouri, Arkansas, and the Indian Terri- 



146 THE CHEMISTRY OF PAPER-MAKING. 

toiy to the valley of the Trinity River, Texas; in central and 
southern Mexico. 

Wood heavy, hard, not strong, rather tough, close grained, 
compact, inclined to shrink and warp badly in seasoning, sus- 
ceptible of a beautiful polish ; medullary rays numerous, very 
obscure ; color, bright brown tinged with red, the sap-wood nearly 
white. 

Easily yields to chemical processes a pulp of short fibre, much 
resembling poplar. 

Cypress (Taxodium distichum). — Sussex County, Delaware, 
south near the coast to Mosquito Inlet and Cape Romano, Florida, 
west through the Gulf States near the coast to the valley of the 
Nueces River, Texas, and through Arkansas to western Tennessee, 
western and northern Kentucky, southeastern Missouri, and south- 
ern Illinois and Indiana. 

Wood light, soft, close, straight grained, not strong, compact ; 
easily worked, very durable in contact with the soil; bands of 
small summer cells broad, resinous, conspicuous ; medullary rays 
numerous, very obscure ; color, light or dark brown, the sap-wood 
nearly white. 

Easily reduced to pulp by sulphite process, unbleached fibre 
rather dark in color, and woolly ; bleaches readily, and then much 
resembles spruce. 

Beech (Fagus ferruginea). — Nova Scotia and the valley of 
the Restigouche River to the northern shores of Lake Huron 
and northern Wisconsin, south to the Chattahoochee region of 
western Florida and the valley of the Trinity River, Texas, west 
to eastern Illinois, southeastern Missouri, and Madison County, 
Arkansas (Letterman). 

Wood very hard, strong, tough, very close grained, not durable 
in contact with the soil, inclined to check in drying, difficult to 
season, susceptible of a beautiful polish ; medullary rays broad, 
very conspicuous ; color varying greatly with soil and situation, 
dark red, or often lighter, the sap-wood nearly white. 

Rather more difficult to reduce than poplar ; fibres somewhat 
shorter ; pulp soft, easily bleached. 

Silver Maple {Acer dasycarpuni). — Valley of the Saint John 
River, New Brunswick, to Ontario, south of latitude 45°, south to 
western Florida ; west to eastern Dakota, eastern Nebraska, the 
valley of the Blue River, Kansas, and the Indian Territory. 



FIBRES. 147 

Wood light, hard, strong, brittle, close grained, compact, easily 
worked ; medullary rays numerous, thin. 

More difficult to reduce than poplar ; fibres somewhat shorter ; 
pulp soft, easily bleached ; rarely used, and only by soda mills. 

Bass Wood (Tilia Americana). — Northern New Brunswick, 
westward in British America, to about the one hundred and second 
meridian ; southward to Virginia, and along the Alleghany Moun- 
tains to Georgia and southern Alabama; extending west in the 
United States to eastern Dakota, eastern Nebraska, eastern Kansas, 
the Indian Territory, and southwest to the valley of the San 
Antonio River, Texas. 

Wood light, soft, not strong, very close grained, compact, easily 
worked ; medullary rays numerous, rather obscure ; color, light 
brown, or often slightly tinged with red, the sap-wood hardly 
distinguishable. 

Very easily reduced, and yields by soda process pulp similar to 
poplar. 

White Birch (Betula alba). — New Brunswick and the valley 
of the lower Saint Lawrence River to the southern shores of Lake 
Ontario ; south, generally near the coast, to Newcastle County, 
Delaware. 

Wood light, soft, not strong, close grained, liable to check in 
drying, not durable ; medullary rays numerous, obscure ; color, 
light brown, the sap-wood nearly white. 

Easily reduced; pulp much resembles poplar. 

Paper Birch {Betula papyrifera). — Northern Newfoundland 
and Labrador to the southern shores of Hudson Bay, and northwest 
to the Great Bear Lake, and the valley of the Yukon River, Alaska ; 
south in the Atlantic region to Wading River, Long Island, the 
mountains of northern Pennsylvania, Clear Lake, Montcalm 
County, Michigan, northeastern Illinois, and Saint Cloud, Minne- 
sota ; in the Pacific region south to the Black Hills of Dakota (R. 
Douglas), the Mullen Trail of the Bitter Root Mountains and 
Flathead Lake, Montana, the neighborhood of Fort Colville, 
Washington Territory (Watson), and the valley of the lower 
Fraser River, British Columbia (Engleman & Sargeant). 

Wood light, strong, hard, tough, very close grained, compact ; 
medullary rays numerous, obscure ; color, brown tinged with red, 
the sap-wood nearly white. 

Somewhat more difficult to reduce than poplar. Pulp easily 
bleached and similar to poplar. 



148 THE CHEMISTRY OF PAPER-MAKING. 

Buckeye (JEsculus glabra). — Western slopes of the Alleghany 
Mountains, Pennsylvania, to northern Alabama, westward through 
southern Michigan (rare) to southern Iowa, eastern Kansas to 
about longitude 97° west, and the Indian Territory. 

Wood light, soft, not strong, close grained, compact, difficult to 
split, often blemished by dark lines of decay; medullary rays 
obscure ; color, white, the sap-wood darker. 

Said to be occasionally used in pulp-making. 

Black Willow QSalix nigra). — Southern New Brunswick and the 
northern shores of Lakes Huron and Superior, southward through 
the Atlantic region to Bay Biscayne and the Caloosa River, 
Florida, and the valley of the Guadalupe River, Texas ; Pacific 
region, valleys of the Sacramento River, California, and the Colo- 
rado River, Arizona. 

Wood light, soft, weak, close grained, checking badly in drying ; 
medullary rays obscure ; color, brown, the sap-wood nearly white. 

Said to be occasionally used in pulp-making. 

Locust (JRobinia pseudacacia). — Alleghany Mountains, Penn- 
sylvania (Locust Ridge, Monroe County, Porter), to northern 
Georgia ; widely and generally naturalized throughout the United 
States east of the Rocky Mountains, and possibly indigenous in 
northeastern (Crowley's Ridge) and western Arkansas and the 
prairies of eastern Indian Territory. 

Wood heavy, exceedingly hard and strong, close grained, com- 
pact, very durable in contact with the ground ; layers of annual 
growth clearly marked by two or three rows of large, open ducts ; 
color, brown or, more rarely, light green, the sap-wood yellow. 

Said to be occasionally used in pulp-making. 

Chestnut (Castanea vulgaris). — Southern Maine to the valley of 
the Winooski River, Vermont, southern Ontario and southern 
Michigan, south through the northern states to Delaware and 
southern Indiana, and along the Alleghany Mountains to northern 
Alabama, extending west to middle Kentucky and Tennessee. 

Wood light, soft, not strong, coarse grained, liable to check and 
warp in drying, easily split, very durable in contact with the soil ; 
layers of annual growth marked by many rows of large, open 
ducts ; medullary rays numerous, obscure ; color, brown, the sap- 
wood lighter. 

Said to be occasionally used in pulp-making. 



FIBBES. 



149 



The following table, from the report for 1890 of the chief of the 
Division of Forestry, gives interesting figures regarding the use of 
the various woods in pulp-making : — 



States. 



Maine 



New Hamp 
shire 



Massachusetts, 



Connecticut 



New York . 



Pennsylvania. 



Maryland 

Delaware 

Virginia 

West Virginia. 
North Carolina 
South Carolina 
Georgia 

Kentucky .... 
Ohio ■.. 



Kinds of wood used. 



12 Spruce only or chiefly. .. 
Spruce and poplar 

1 Spruce, poplar, and pine 
1 Poplar 

13 Spruce only or chiefly . . 



Spruce and poplar 

Spruce ouly or chiefly , 



Spruce and poplar 

Poplar and pine 

Spruce only or chiefly 



Spruce and poplar. 
Spruce 



Spruce only or chiefly 
Spruce and poplar. . . . 



Spruce and hemlock 

Spruce, hemlock, hass. . . 
Spruce, poplar, and pine 

Poplar 

Poplar, bass, pine, and 
spruce. 

Spruce and pine 

Spruce only or chiefly 
Spruce and poplar 



Poplar 



Poplar, hass, piue 

Poplar, bass, pine, maple 
Hemlock, pine, beech, 
bass. 

White pine 

Spruce only or chiefly. .. 



Poplar 

Poplar 

Poplar 

Spruce only or chiefly. 

Pine 

Cypress and gum 

Pine 

Cypress and gum 



Spruce, buckeye, and 

maple 

Spruce only or chiefly. .. 
Cottonwood and bass 



Range of yield, per 

cord, in hundreds 

of pounds. 



16-20 
15-20 



20-23 

20 

15-22 



15-22 
16-20 



10 

10.3 



9-10 

7-12 

10 



11-13.5 



Number of 
mills re- 
porting 
supplies. 



Remarks. 



1 gets supplies mostly 
from Canada. 

2 get supplies partly 
from Canada. 

1 gets supplies mostly 
from Canada. 



2 supplies fromNorth- 
ern Vermont and 
New Hampshire. 

Supplies from New 
Brunswick and 

Nova Scotia. 

1 supplies mostly 
from Canada. 

15 supplies from Can- 
ada or distant points. 



Supply from West 
Virginia and Nova 
Scotia. 

Supply from Mary- 
land and Virginia. 



Spruce from West 
Virginia and Can- 
ada. 



150 



THE CHEMISTRY OF PAPER-MAKING. 





a 



,o 

S 

3 

fe 

3 
1 
2 
1 

1 
1 
4 

3 

4 

1 

4 
15 
4 
1 
1 
1 


Kinds of wood used. 


Range of yield, per 

cord, in hundreds 

of pounds. 


Number of 
mills re- 
porting 
supplies. 




States. 


"a 

a 
,£3 
o 


T3 
O 

GO 


6 

3 

m 




o 
1 


'3 
i 


-6 

s 

i 
i 


be 
c 

P 


3 
o 
Pj 

2 
1 

1 
2 


Remarks. 






16 
16 
12 
10 

20 










Aspen, poplar, cotton- 
wood. 


























i 
i 


1 

1 
1 

2 








9 


\ 

2 
4 


2 






Spruce only or chiefly . . . 


16 

16-20 


15 


8-10 


1 supply all from 
Canada. 




Poplar, pine, tamarack, 
spruce, and balsam. 

Aspen, pine, poplar, 
spruce, and bass. 

Spruce only or chiefly . . . 

Spruce and poplar 

Spruce only or chiefly . . . 






14 

16-18 

13-15 

10-12 

15 








Wisconsin — 
Minnesota .... 




9-10 
9-10 


1 

5 
1 


2 

5 


2 
1 
1 








1 

1 






Tamarack and fir 


17 









PROCESSES FOE ISOLATING CELLULOSE. 151 



CHAPTER III. 

PROCESSES FOR ISOLATING CELLULOSE. 

Rag- Boiling-. — In order to free the rags from the dirt and other 
impurities with which they are generally associated as received at 
the mill, they are put through a preliminary mechanical treatment, 
and are then boiled, usually under pressure, with alkali. The pre- 
liminary treatment involves the threshing, picking, cutting, and 
sorting of the rags, opening seams to facilitate removal of dirt, 
carefully removing all buttons, metallic fasteners, rubber, and such 
foreign materials, a final cutting by machinery into pieces about 
two inches square, and dusting. Such severe treatment is, of 
course, unnecessary in the case of new cuttings, which contain 
merely a moderate admixture of starch, clay, and similar sub- 
stances employed in sizing and filling, and such rags are often put 
directly into the engine and beaten up when strength is especially 
desired. 

The object of the boiling operation, to which all other rags are 
subjected, is to bring the grease, dirt, and other impurities into 
such condition that they may subsequently be easily removed by 
washing, and to destroy or so affect the coloring-matter as to 
facilitate the process of bleaching. Lime is only slightly soluble 
in water, 1 part, in the cold, dissolving in 425 parts of water, but 
it forms, with the acids of the grease, insoluble soaps, and as these 
are precipitated, fresh portions of the alkali pass into solution. In 
the case of soda, the soaps formed are soluble, and therefore more 
easily washed out ; but the action of this base, in strong solution, 
upon the fibre is more severe, and it is believed to occasion greater 
loss. 

The rotaries commonly employed are of the well-known cylin- 
drical, horizontal type, turning about once a minute, and of various 
dimensions. They are fitted with manholes and with steam-pipes, 
the latter passing through the trunnions and curving below them. 
The rotary is packed with rags, and milk of lime is run in through 
a sieve, which may be made of a piece of Fourdrinier wire ; water 



152 THE CHEMISTRY OF PAPER-MAKING. 



is added in amount sufficient to come above the journals, or even 
in some cases to fill the boiler two-thirds full, the manholes are 
closed, and in the best practice the rotary is allowed to run for 
half an hour before steam is admitted. The lime used should 
contain as little iron as possible, and is best suited for this purpose 
when the content of magnesia is small, since this base is practically 
insoluble in water, and is much less powerful in its action than 
lime. The lime should slake readily and completely, and should 
be so kept as to avoid air-slaking. We give below an analysis of 
an excellent grade of lime for this purpose : — 

Per cent. 

Silica, etc., insoluble in acid 0.01 

Iron and alumina (Fe 2 3 and A1 2 3 ) . . . 0.28 

Lime (CaO) 92.81 

Magnesia (MgO) 2.28 

Moisture, carbonic acid, etc. (by difference) 4.62 

Total , 100.00 

The proportion of lime used, as well as the pressure and time of 
boiling, depends very much upon the character of the rags treated 
and the amount and kind of dirt which they contain. From 5 to 
18 per cent, of lime on the bale weight of the rags are the extremes, 
the general tendency being toward the higher limit. For No. 3 
cottons and blues about 15 per cent, of lime is used ; for shivy 
linen 15 to 18. A pressure of 60 to 80 lbs. of steam is usually car- 
ried, and the time of boiling extends from twelve to eighteen hours, 
though the details of treatment vary not only with the stock, as 
just stated, but also in different mills. The paper-maker is 
governed by the stock he has and the paper he has to make. The 
better grades of rags require less time, pressure, and lime, and are 
in many mills boiled in open bleaches. 

In emptying the rotaries the practice also varies. Some super- 
intendents blow the pressure down completely before opening the 
bottom blow-off to run off the liquor prior to opening the man- 
holes ; while others, as we believe with good reason, reduce the 
pressure to 20 or 30 lbs., and blow the liquor off under this 
pressure through the bottom valve, claiming thereby to carry away 
more dirt. An objection to this procedure is found in the danger 
of losing some fine fibre in the blow-off. As soon as the liquor has 
left the rags, they are dumped upon the floor to drain. The empty 
ing is performed with as much expedition as possible, in order that 



PROCESSES FOR ISOLATING CELLULOSE. 



153 



the liquor, which contains substances more readily soluble in hot 
than in cold water, may carry these off before it cools. The rags 
are softened if they are allowed to remain piled up on the floor for 
several days. 

Japanese rags are washed and spread upon the grass at the 
country of shipment, and seed hulls thus derived may cause 

LONGITUDINAL SECTION 




Fig. 9. — The Mather Kiek. 



trouble. They may be reduced by the addition of 1 per cent, of 
soda-ash on the weight of the rags. Such addition of soda-ash, in 
the proportion of 1 to 5 per cent., greatly increases the efficiency 
of the liquor in its action upon certain colors, as for instance red, 



154 



THE CHEMISTRY OF PAPER-MAKING. 



which is usually difficult to destroy, and which may even leave a 
tinge of that color in the bleached half-stuff. Japan blues give a 
bluish tinge suitable for white papers, while the darker shades of 
natural may be as well made from city rags, which are usually 
darker than those from the country. Such considerations are 




'mmm^^mm^m^^flik 



% 



1 



Fig. 10. — The Mather Kier. 



borne in mind by the superintendent in sorting and mixing the 
rags prior to boiling. 

The Mather Kier. — This well-known apparatus, which is 
shown in Figs. 9 and 10, was originally designed for the bleaching 
of textiles, and its adoption by the leading bleachers of cloth all 



PROCESSES FOR ISOLATING CELLULOSE. 155 



over the world has demonstrated its value in this direction. It 
has lately been applied to the boiling of rags for paper-making at 
the mill of W. Joynson & Son in England, and the results there 
secured are such as to merit the attention of American paper- 
makers. 

The kier consists of a horizontal boiler closed in front by a 
door, E, which is the full diameter of the kier. This door is 
balanced by the counterpoise, 6r, and is raised, lowered, and set 
up against the seat by hydraulic power. On the bottom of the 
kier are tracks upon which can be run in two cars, A, A, contain- 
ing the cloth or rags. Owing to the construction of the kier and 
the mode of operation the amount of liquor required is very small. 
The liquor is drawn from the bottom of the kier through D by the 
pump, P, and is discharged upon the rags through the inlets, C, C, 
above the spreaders, B, B. 

The results obtained in the treatment of rags in practice are best 
set forth in the report of Messrs. Cross and Bevan, which is given 
in large part below : — 

A kier was erected last year [1888] at the works of Messrs. W. Joynson & 
Son, St. Mary Cray, where it has been in continual use for six months. Its 
dimensions are 8 feet long by 7 feet in diameter, and it is adapted to hold two 
wagons. In order, however, to economize time, six wagons are employed by 
Messrs. Joynson, four either being filled or washed, while the other two contain 
rags in process of treatment in the kier. The cut and dusted rags are delivered 
automatically from a shoot direct into the wagons. The average weight taken 
by each wagon is 16 cwt., the full kier charge being therefore 32 cwt. The run- 
ning of the wagons into the kier and the closing of the patent door occupy only 
some two or three minutes. As soon as this is completed, the rags are saturated 
with about 750 gallons of caustic-soda solution, which is delivered from a tank 
above the kier, and is circulated by means of a centrifugal pump. Steam is 
turned on until the pressure reaches 10 lbs. per square inch, and the process 
continued for from two to three hours according to the nature of the material. 
The steam is blown off, which occupies about fifteen minutes, the door opened, 
the wagons removed, and another pair run in, the three latter operations occupy- 
ing only ten minutes. 

The rags, after being withdrawn from the kier, are washed by causing cold 
water to flow on to the top of the wagons. By performing this operation out- 
side the kier a considerable saving of steam is effected, only one heating up of 
the kier being required. Arrangements are provided for washing the rags by 
upward displacement, by which a further economy of water is effected. 

The kier in use at Messrs. Joynson's is capable of doing at least 40 tons of 
rags per week : it has, in fact, for some time past been used for treating the 
whole of the rags used in the mill. It is equally well adapted, with certain 



156 THE CHEMISTRY OF PAPEE- MAKING. 

slight modifications of treatment, for all classes of rags, from new linen and 
cotton pieces to unbleached linen. 

The labor required is one man for "treading" the rags into the wagons, one 
man for tending the kier, mixing the liquors, etc., and one man for emptying 
the wagons. Where circumstances permit, the wagons can be hoisted and 
transferred direct to the side of the breaking engines, thereby saving the labor 
of emptying into trucks. 

The following are among the further advantages claimed for the kier, and 
substantiated by the result of the extended trial by Messrs. Joynson & Son : — 

1. The rags, being stationary during the steaming, are never " knotted," as is the 
case with revolving boilers ; they can therefore be rapidly filled into the 
breakers without danger to the breaking rolls. 

2. A notable improvement in the color of the rags, after treatment, both before 
and after bleaching. This would enable the paper-maker to use rags of some- 
what lower quality, without affecting the color of his paper. If an improved 
quality of pulp is not so much desired as economy of chemicals, a saving 
of about 25 per cent, of the latter can be effected. It amounts on the average 
to Is. 3d. per ton of rags for soda, and about 2s. for bleaching-powder. It 
has, however, been found more advantageous to forego this saving and aim 
at improved quality of pulp instead. 

3. Economy of water for washing purposes, 1000 gallons being sufficient for one 
ton of rags, as against four or five times this amount by the ordinary process. 

4. Saving of steam for heating and maintenance of steam pressure. This has 
been found to amount to about one-third of that required by the best system 
of treatment in revolving boilers, or about 6d. per ton of rags, with coal at 
15s. per ton. 

5. Improved strength of fibre. It has been abundantly proved in the case of 
cotton and linen textiles that a notable increase in strength is obtained by 
the use of the kier as compared with any other form of boiler. It may fairly 
be assumed, therefore, that the fibres suffer less damage from the action of 
the alkali in the case of rags also. 

6. An enormous saving in the space occupied. A kier 8 feet long by 7 feet 
diameter occupies, with turntables, rails, etc., for four extra wagons, engine 
for driving pumps, etc., a ground space of 727 square feet. To this should 
be added the space occupied by the overhead tanks for the caustic soda, 
making a total of 843 square feet. The ground space occupied by six boilers, 
required to treat the same amount of rags, would amount to 1440 square feet. 
In addition to this a top floor of equal area would be required for filling. 
Together these amount to 2880 square feet, as against 813 square feet 
required for the kier. 

Treatment of Picker Seed and Picker Waste. — These two 
raw materials require about the same treatment. They are boiled, 
either in rotaries or open tubs, with rather weak lye. About 
125 lbs. of soda-ash and 150 lbs. of lime are used to the ton of 
stock. Treatment in the rotary requires about 65 lbs. pressure if 



PROCESSES FOR ISOLATING CELLULOSE. 



157 



the boiling is to be completed in about eight hours. Twelve hours 
in the open tub gives a stock which bleaches better than that 
obtained by boiling under pressure. In either case the stock is 
much improved by being allowed to stand from six to eight days 
to soften. The same treatment applies to Cotton Waste. 

Treatment of Esparto. — On account of the high price of this 
material it has never successfully come in competition with poplar 




Fig. 11. — Vomiting Boiler. 



fibre in this country, but on the Continent, and especially in Eng- 
land, it forms one of the most important sources of paper-stock. 
The grass is first picked over by hand to remove root ends, weeds, 
etc., and is then shaken and dusted. It is packed into the boiler 
without cutting, as is the case with straw. The details of the 
boiling operation vary much in different mills. In a few cases 
open vomiting-tubs are used, but the general practice is to treat, 
under pressure, in vertical boilers. In rotaries the fibre is likely 



158 THE CHEMISTRY OF PAPER-MAKING. 

to roll up into small balls, which make lumps in the paper. The ' 
pressures carried vary from 5 to 50 lbs., and the time of boil- 
ing is from one and a half to six hours. Caustic-soda liquor is 
always used. Routledge gives 10 per cent, of soda as the neces- 
sary amount. In one of the best English mills the practice is to 
use 16 lbs. of caustic per 112 lbs. of grass, and to boil from 
one and a half to two hours at 40 lbs. pressure. 

One of the best types of boiler for esparto is shown in Fig. 11. 
It is a vomiting-boiler, the steam, which is admitted through A, 
passing to the bottom of the boiler before escaping. It then drives 
upward through the vomit-pipe, G 7 , carrying with it the liquor 
which has worked below the false bottom, B, B, and which is then 
discharged under the hood, D, which acts as a spreader. F is the 
manhole for filling, the manhole plate being secured by the clamps, 
F, F, and balanced by the counterpoise, L. The boiler is emptied 
through H. if is a safety-valve. 

The washing of the pulp and recovery of the liquors are gener- 
ally conducted as in soda-pulp mills in this country, but we have 
been in at least one English mill where no attempt at recovery was 
made. In many others the old-style pan evaporators are in use, 
but they are being replaced by the far more economical multiple- 
effect Yaryans. The ash in esparto is over 3 per cent., and consists 
largely of silica, which forms silicate of soda in the furnacing of 
the liquors, and thus reduces somewhat the per cent, of ash re- 
covered. A recovery of about 80 per cent, is claimed. Recent 
experiments seem to show that it is impossible to recover over 85 
per cent, under the best conditions. The yield of fibre is about 
50 per cent., and it is bleached to good color with 7 per cent, of 
bleaching-powder. 

Treatment of Straw. — The similarity between the plant sub- 
stance of straw and that of esparto is sufficiently close to render 
substantially the same methods of treatment applicable to both. 
Straw is, however, rather more highly lignified, and on that ac- 
count requires the employment of somewhat higher pressures, 
or of stronger solutions. In the preliminary treatment, the straw 
is picked over by hand to remove weeds, etc., and is afterwards 
dusted and cut into small pieces one to two inches long. Care is 
taken to avoid the presence of seeds or seed hulls in the material 
ready for the boiler, as these are reduced with difficulty, and are 
likely to form specks in the pulp. 



PROCESSES FOR ISOLATING CELLULOSE. 159 

The different processes for treating straw show considerable 
variation in their details, according to the kind and quality of 
the straw itself, and the purpose for which the product is to be 
used. They nearly all show in their general principles a close 
resemblance to the process of Mellier, patented in 1854, and which 
consisted in cooking the straw, for about three hours, at a pressure 
of 70 lbs., with a solution of caustic soda contained in a rotary 
digester heated by indirect steam: 16 lbs. of caustic were used 
per 100 of straw. 

Most of the straw pulp made in this country is prepared for use 
in strawboard by boiling the straw with lime. Abroad the straw is 
more commonly treated for the production of the pure fibre. The 
following methods are among those used in Germany : — 

1. A charge of about 700 kilogrammes of straw is packed into a 
rotating spherical digester of 235 cm. diameter. Liquor is used 
which contains about 13 per cent, caustic soda figured on the weight 
of the straw, and the digester is rotated cold from one to three 
hours. The boiling is carried on from six to eight hours, at about 
40 lbs. pressure. 

2. A charge of 1000 kilogrammes of straw is extracted from 
one to three hours with warm water, which is then drained off and 
the leaching repeated. The mass is then drained and packed into 
a cylindrical rotary. The lye is made by dissolving 10 to 14 per 
cent, caustic-soda, calculated on the gross weight of the straw, in 
only enough water to well wet but not to cover the straw. The 
cooking is carried on from four to six hours, at a temperature of 
about 150° C. After dumping, the pulp is washed for eight to 
twelve hours with warm water. 

3. A charge of 1000 kilogrammes more or less of straw is 
packed and tamped into bags holding 40 to 60 kilogrammes each. 
The bags are tied up and packed in a cylindrical rotary. The 
cooking is carried on from four to eight hours with a caustic liquor 
standing 5° to 8° Be. The pressure varies from 75 to 120 lbs. 
These variations in treatment are rendered necessary by the quality 
of different straws and the character of pulp desired. 

4. In order to obtain a strong, creamy white fibre for use in fine 
writing-papers the straw is cut very small, and carefully cleaned 
from all weeds. Small spherical or cylindrical rotaries are used. 
The straw is first cooked for five to eight hours, at about 60 lbs. 
pressure, with 13 to 17 per cent, of lime, and sufficient water is 



160 



THE CHEMISTRY OF PAPER-MAKING. 



used to keep the straw covered. It is then dumped into washing- 
engines fitted with granite plates, and carefully washed and beaten 
in order to remove all the lime with as little injury to the fibre as 
possible. The stuff is kept in drainers for about four days in order 
to make it soft and porous, and is then cooked for about five hours, 
at 40 lbs. pressure, with a soda lye containing 6 per cent, of caustic 
soda on the weight of the straw. 

The mechanical preparation of the straw before cooking and the 
treatment to which it is afterwards subjected have at least as much 
to do with the quality of the product as the details of the boiling 
operation. 

Some manufacturers find an objection to the use of rotary boilers, 
in the liability of the short fibres to roll up into little balls, which 
are likely to make spots in the paper. Partly on this account, and 
partly because of a real or supposed economy of soda, vomiting- 
boilers are in use in some mills abroad, especially in England. 

In order to pack the greatest amount into the rotary the digester 
is, in some cases, filled with the chopped straw, and then run for a 
few moments with a portion of the liquor, so that the straw may 
soften and pack down sufficiently to admit a considerable addi- 
tional quantity. The English practice in boiling shows the varia- 
tions noticed elsewhere. According to Cross and Bevan the pro- 
portion of caustic is from 10 to 20 per cent, of the weight of the 
straw, and the boiling is carried on from four to eight hours, at 

pressures ranging in the different 
mills from 10 to 50 or even to 
80 lbs. 

Glaser, British patent No. 938, 
A. d. 1880, subjects the straw pulp 
obtained by the usual process of cook- 
ing to the action of chlorine gas, in 
leaden or stone chambers, for several 
hours. A very complete isolation of 
the cellulose is thus secured, but the 
pulp has afterwards to be bleached 
in the ordinary way in order to free 
it from all products of the chlorine treatment. 

Considerable rye straw is still treated in France by the following 
method for the manufacture of a coarse pulp : The straw is cut 
quite short in a cutting-machine. It is then transferred into large,. 




Fig. 12. — Edge-Runnee. 



THE MANUFACTURE OF WOOD FIBRE. 161 

rectangular brick wells, and just covered with dilute milk of lime. 
A covering of heavy boards weighted with stones is put on, and 
the whole allowed to remain from two to four weeks. The mass 
of pulp is then removed and worked under edge-runners (Fig. 12) 
for not less than an hour. As the knots are not softened, especial 
care must be taken to have the grinding well done. The product 
is harder than that from straw which has been treated in the usual 
way. 

On account of the considerable proportion of silica present in 
straw, it has been generally assumed that this material would not 
easily lend itself to treatment by the sulphite process. Practical 
experience has, however, shown that this is not the case, and this 
process has recently been applied to the preparation of straw pulp 
with excellent result. 



THE MANUFACTURE OF WOOD FIBRE. 

The Soda Process. — The efficiency of this process depends 
partly upon the direct solvent and saponifying power of the alkali 
at high temperatures, and partly upon the secondary reactions, by 
means of which the acid products resulting from the resolution of 
the wood are brought into the liquor as salts of soda. Mere treat- 
ment in the cold with dilute alkali is sufficient to dissolve an 
appreciable portion of the incrusting matter of wood, and the sol- 
vent power of the alkali is greatly enhanced as the temperature 
rises. 

Poplar is used far more than any other wood in the soda proc- 
ess, but considerable quantities of pine, spruce, and hemlock are 
consumed in making longer fibred stock, while such woods as 
maple, cottonwood, white birch, and basswood are not infrequently 
made to replace poplar. Maple, birch, and basswood, however, 
give so short a fibre when used alone that they are generally 
mixed with poplar. 

On account of the great solvent power of the alkaline solution, 
comparatively little pains are necessary in the preparation of the 
wood. The bark is removed, but no attempt is made to take out 
knots or portions which are stained or rotten. The process reduces 
small fragments of bark and knots to pulp. Whole knots are 
somewhat softened, but are easily removed by the screens. The 



162 THE CHEMISTRY OF PAPER-MAKING. 

wood is always chipped in the well-known manner, and the chips 
in the best practice are either sent through a willow duster or 
blown against a wire netting to remove the dirt which collects 
upon the piled wood. 

The digesters used in this process are all of well-known forms. 
The most common type is probably a horizontal cylindrical rotary, 
about 22 feet long by 7 in diameter, and holding about three cords 
of wood. Such digesters are usually heated by coils supplied with 
steam through the trunnions, and revolving with the boiler. A 
few spherical rotaries are used, a common size being 12 feet in 
diameter, with a capacity of about five cords. Many mills use 
upright digesters, a few of which are heated by a steam-jacket, as 
in the Marshall boiler, a few by direct fire, but by far the greater 
number by live steam. It is very difficult to keep an iron shell 
tight in which alkaline solutions are boiled, as such solutions soon 
work their way through crevices which would be tight to water. 
Leaky digesters have in the past been a source of much annoyance 
in this process, but at the present time comparatively little diffi- 
culty from this cause is experienced. The Marshall jacketed 
boiler rested its claims chiefly upon the fact that the pressure in 
the jacket was always kept higher than that in the digester, so that 
in case of any leak in the digester walls there was a passage of 
steam inward rather than a passage of liquor outward. A welded 
digester is now upon the market, which would seem to make 
further trouble from leakage unnecessary. 

The strength of liquor used varies from 8° to 15° Be*, at 60° F., 
according to the pressure and time of boiling and the manner in 
which heat is applied to the digester. Where heating is effected 
by jackets, coils, or direct fire, the liquor ordinarily stands from 
12° to 14° Be\, and contains, when properly causticizecl, from 6 to 9 
per cent, of caustic soda, NaOH. With live steam allowance has 
to be made for condensed water, and it is necessary to use less 
liquor, but of higher test. With indirect heat in rotaries about 
700 gallons of liquor are used to a cord of wood. Upright digesters 
require considerably more, or enough in any case to cover the wood 
as soon as it becomes well soaked and settles down. 

As much wood as possible is put into the digester, and in some 
cases mechanical devices for tamping and packing the wood are 
employed. 

The boiling operation is a simple one. Full pressure is reached 



THE MANUFACTURE OF WOOD FIBRE. 163 



as soon as possible, and is maintained to the end of the cook. Watt 
and Burgess are said to have used a lye of 12° Be., at a pressure of 
60 lbs., but the later experience has been that even 75 lbs. is not 
sufficient to ensure a good cook, and the tendency now is toward 
the adoption of pressures above 100 lbs. With 90 lbs. as a mini- 
mum the present practice generally calls for 100 to 110 lbs. pres- 
sure. The time of boiling is eight to ten hours. As the pressure is 
increased, the strength of the liquor may be somewhat diminished. 
Thus Houghton, in the early days of the process, used a lye of 
4° Be., at pressures which reached 180 lbs. 

The practice necessarily varies with the character of the wood to 
be treated, and where 11° Be. gives good results with poplar, maple, 
cottonwood, or basswood, a lye of 15° Be. is needed for spruce, 
pine, or hemlock. The experiments of Tauss have shown that an 
increase in the time of boiling is only a partial equivalent for the 
use of such stronger liquors. 

The pulp obtained at the close of the cook is of a grayish brown 
color, while the liquor is a dark, rich brown, and has a somewhat 
empyreumatic odor. It contains very little alkali which is not in 
combination with the acid products from the wood. The contents 
of the digester are dumped or blown into one of a series of iron 
washing-tanks, with drainer bottoms, and the pulp is there sub- 
jected, after most of the liquor has drained off, to a thorough and 
systematic washing. It is extremely important to remove the last 
traces of black liquor with as little expenditure of water as possi- 
ble, because even a small quantity of such liquor left in the pulp 
renders bleaching very difficult ; while, if a large quantity of water 
is used, the cost of concentrating the liquors in the recovery proc- 
ess becomes excessive. For these reasons the pulp in the different 
tanks is washed with the liquor coming from the tank before it in 
the series, and the moderate quantity of fresh water which finishes 
the washing of one lot of pulp passes in succession through four or 
five tanks, in each succeeding one of which the quantity of black 
liquor in the pulp is greater, until finally it passes through the 
pulp which has just come from the digester, and is brought up to 
about one-half the strength of the original liquor. 

Well-washed poplar pulp made by this process bleaches easily 
with 12 to 14 lbs. of bleaching-powder to the hundred, and then con- 
sists of almost entirely pure cellulose. An appreciable portion of 
the cellulose present in the wood is dissolved during the boiling, 



164 THE CHEMISTRY OF PAPER-MAKING. 

and the yields are consequently lower in this than in the sulphite 
process. Differences of treatment and inaccuracies in the measure- 
ment of wood make the yields reported by the different mills vary 
to a considerable extent, as is shown by the table on page 149. 

Unbleached spruce pulp is soft and strong, but the coloring- 
matter derived from the decomposition of the non-cellulose por- 
tion of the wood so nearly approaches tar or ulmic compounds in 
character that it can only be bleached to good color by an oxidizing 
treatment so severe as to attack and weaken the cellulose itself. 
For this reason most of the spruce pulp is used in papers of such 
grades or tints that its color is no objection. 

Recovery of Soda. — In the early days of the process no attempt 
was made to recover the soda from the waste liquors, but the 
nuisance caused by their discharge into running streams, and the 
large quantity of ash required, soon led to the adoption of various 
methods of reclaiming. The character of the waste liquor and the 
combinations in which the soda exists therein are such as to render 
recovery especially easy from a chemical point of view. The or- 
ganic acids with which the soda is combined, as well as the organic 
matter present in other forms, represent nearly one-half the fuel 
value of the original wood, and furnish by their combustion a 
supply of heat which, if utilized in a properly constructed appara- 
tus, is nearly or quite sufficient to effect the concentration of the 
weak liquors up to the point where they may be ignited. After 
the ignition in the presence of so much carbonaceous matter, the 
soda remains as carbonate in the black ash. 

Among the bodies which have been recognized in the black 
liquor are sodium formate, oxalate, and acetate, together with dark- 
colored products similar to ulmic acid. Sugar and bodies like 
sugar are not present. According to Tauss the proportion of sub- 
stances which are precipitated by alcohol and acids becomes 
greater as the pressure or the concentration of the lye is in- 
creased. 

Where the original boiling liquor was strong, and where much 
care is taken to wash the pulp in a systematic manner, it is possi- 
ble to bring the mixture of waste liquor and wash water up to a 
gravity of 6° to 9° Be. at 160° F. The higher gravity is very rarely 
reached, and in some mills the liquors going to the evaporator do 
not stand over 3° to 4° Be\ at the same temperature. The follow- 
ing analysis of a partially concentrated liquor indicates in a general 



THE MANUFACTURE OF WOOD FIBRE. 



165 



way the proportion between the organic and inorganic constituents 
of liquors of this class : — 

Black liquor standing 111° Be. at 115° P. 

Per cent. 

Water 83.51 

Organic matter 5.96 

Caustic soda 8.60 

Black ash waste 1.93 

Total 100.00 

In order to maintain a continuous combustion of the organic 
matter, the liquor must be concentrated by evaporation until it 
stands at least 30° Be. at 130° F., and it is desirable to bring up to 
40° Be. or even higher. 

In the earliest systems of recovery the evaporation was con- 
ducted in open pans, frequently arranged one above the other to 
avoid undue loss of heat, but the volume of liquor to be concen- 
trated is so large that such crude forms of apparatus, in which only 
a small proportion of the heating power of the combustible is made 
efficient, have now been almost entirely replaced by forms in which 
the principles of multiple-effect evaporation are embodied. 

The boiling-point of water depends, as is well known, upon the 
pressure under which evaporation takes place, and is rapidly 
lowered as the pressure is diminished. Under the ordinary atmos- 
pheric pressure of 14.7 lbs. the boiling-point is 212° F. 

The lowering of the boiling-point of water by diminution of 
pressure is shown by the following table : — 



The temperature of water boiling — 
at atmospheric pressure is 
under 5 ins. vacuum is 
" 10 " " 

•" 15 " " 

'- 20 " " 

" 25 " " 

a 26 " " 

a <)j a u 

u 28 " " 

a 90 a (C 

tt 291 " " 



o p 

212 
195 
185 
160 
150 
130 
120 
112 
100 
72 



166 



THE CHEMISTRY OF PAPER-MAKING. 



Other liquids follow a similar rule, but have different normal 
boiling-points ; while, in case of water-holding substances in solu- 
tion, the boiling temperature for the different pressures is increased. 

When water is boiled under the ordinary atmospheric pressure, 
the resulting steam, like the water, has a temperature of 212° F., 
and the large quantity of heat necessary to convert the water into 
steam has been expended in bringing about that complete separa- 
tion of the molecules which constitutes the essential difference 
between steam and water. That portion of the heat which was 
thus consumed or converted into the energy of steam is termed 
latent heat, and reappears when the steam is condensed. The total 




Fig. 13. — The Yaryan Evaporator. 



heat present in a pound of steam at 212° F. is represented by 
1146.1 thermal units, and of this quantity 964.3 thermal units are 
in the form of latent heat. This series of facts is made use of in 
multiple-effect evaporation in the following way: The effects, as 
they are called, are pieces of apparatus so arranged that the steam 
or vapor from the liquid boiling in the first effect can be carried 
over and used as the heating agent in the second effect. The boil- 
ing-point of the liquid in the second effect, and consequently the 
temperature of the vapor issuing from it, is lowered by the main- 
tenance of a partial vacuum in the second effect. The vapor from 
this effect is in the same way used as the heating agent in the third 
effect, in which the boiling-point of the liquid there present is still 
further reduced by the maintenance of a higher vacuum. Three or 



THE MANUFACTURE OF WOOD FIBRE. 



167 



four effects are the number which are ordinarily used in practice, 
but there is in theory no limit to the number which might be used. 
Each additional effect within practical limits increases, in a numer- 
ical ratio, the quantity of liquor evaporated by given weight of 
combustible, because in each effect after the first the vapor from 
the preceding one is made to give up its latent heat to the liquor 
in that effect. 

Many different types of multiple-effect evaporators have been 
devised, but at the present time nearly all the work of evaporat- 
ing soda liquors in this way is done by the apparatus known 
as the Yaryan evaporator, from its inventor. Figure 13 shows 
a triple-effect Yaryan evaporator, as ordinarily designed for soda 
liquors, and Fig. 14 gives a section through one effect. Each effect 
consists of a boiler shell surrounding a number of independent 




Fig. 14. — The Yaryan Evaporator. 

pipes arranged in coils parallel with the length of the shell. The 
pipes are three inches in diameter, and the liquor is admitted into 
each coil through an independent supply tube of relatively small 
diameter, and at the back of the apparatus. The tubes in the first 
effect are heated by steam under a pressure varying in different 
mills from 10 to 45 lbs., and which is admitted into the shell or 
jacket which surrounds the coils. The small stream of liquor 
entering at the back end of a coil is exposed to the action of heat, 
partly as a spray and partly as a thin film lining the interior of the 
tube. Under the influence of the partial vacuum maintained in the 
separating-chamber in Avhich the coil ends, the liquid moves for- 
ward through the coil with considerable velocity, and is thus con- 
tinually exposing fresh particles to the action of the heat. Five 
lengths of pipe constitute a coil, and the liquor, in passing through 
one effect, has therefore to travel a distance equal to about five 



168 THE CHEMISTRY OF PAPER-MAKING. 

times the length of the shell, or 60 feet. The mixture of vapor and 
liquor issuing from each of the independent coils is discharged into 
the separating head or chamber, which forms the front of the effect, 
and there strikes a series of dash-plates or partial partitions, the 
openings through which alternate in such a way that the vapor and 
liquor strike upon each plate in succession, and are at last Avell 
separated, the liquor falling into the drum below the separator, and 
the vapor passing over into the shell or jacket of the second effect. 
The partially concentrated liquor from the first effect is delivered 
into the coils of the second effect through the supply tubes at the 
back, and on its passage through the coils is heated by the vapor 
given off during its concentration in the first effect. As the tem- 
perature of this vapor is lower than that of steam first used, the 
boiling-point of the liquor in the second effect is reduced by the 
maintenance of a slight vacuum. The liquor passes in succession 
through each of the effects, and the vapor from each effect, passes 
over into the shell of the next one, where it is used as the heating- 
agent, each effect being under a higher vacuum than the one pre- 
ceding, in order to compensate for the gradual fall in the tempera- 
ture of the vapor. The vacuum is maintained by means of a con- 
denser and pump ; while, by another pump, the concentrated liquor 
is removed from the last effect. The liquor enters the apparatus 
in a continuous stream at from 3° to 8° Be., and in a few moments 
has passed through the entire system of pipes and been discharged 
at a density of 35° or more : 42° Be. is reached at times, but it is 
difficult to pump liquor standing as high as 40°. The efficiency of 
the Yaryan is said to be due in part to the much greater rapidity 
with which liquids absorb heat when in motion, as compared with 
the rate of absorption when they are at rest. Jelinck gives the 
following 1 figures in this connection : — 



Velocity of the liquid per 
secoud in metres. 


Calories absorbed per 
square metre. 


0.312 


22.7 


0.640 


33.6 


1.020 


46.9 


1.640 


69.9 



The Yaryan evaporator, in connection with the Warren rotary 
furnace, has practically revolutionized the recovery of soda, since 
the expense is not only greatly diminished, but on account of the 
small cost of evaporation the washing can be carried further and 



THE MANUFACTURE OF WOOD FIBRE. 169 

a considerably greater percentage of soda recovered. Under the 
best present practice about 2100 gallons of liquor come to the 
Yaryan per ton of pulp produced, but in some cases the volume 
reaches 3200 gallons per ton. 

The Gaunt multiple-effect evaporator, which is a more recent 
type of apparatus, has been lately applied to the concentration of 
soda liquors. The liquor to be evaporated and the heating agent 
occupy, in this apparatus, positions which are just the reverse of 
those in which they stand to each other in the Yaryan ; that is, the 
liquor flows by gravity over the outside of the pipes in a thin 
sheet, and the vapor from which heat is derived is inside the pipe. 
Where three or four effects are used, they are arranged one above 
the other. The first effect is the highest one, and the liquor fall- 
ing through this collects in the bottom of the effect, and flows into 
the slotted liquor-supply tube of the second effect, which is im- 
mediately below, and so down through the series until it reaches 
the bottom of the last effect, from which it is removed by pump- 
ing. The first effect is heated by direct or exhaust steam, which 
is let into the tubes under a slight pressure, and the vapor formed 
as the liquor falls over the tubes expands into the chamber, in 
which they are enclosed, and passes over into the tubes of the 
second effect ; the vapor from this effect passes into the tubes of the 
one following, and so on. The amount of vacuum maintained on 
each effect is regulated by the height of the liquid seal formed by 
the liquor in the bottom of each effect. The vapor from the last 
effect passes over to the condenser, which maintains the vacuum. 

Partly on account of the thick and tarry nature of the highly 
concentrated liquors, which retards their motion through an 
evaporator and makes pumping difficult, and partly because of 
the tenacity with which the last portions of water are held by the 
dissolved substances, the evaporation of such liquors cannot be 
economically carried above 40° Be. The amount of water still 
present is too great for the liquors to maintain their own com- 
bustion, but when run into a furnace, through which the flames 
from a fire-box pass, they soon take fire and greatly increase the 
amount of heat which would otherwise pass from the furnace. 
The earliest style of black-ash furnace consisted of a pan, over 
which the flames from the fire-box passed as in the reverberatory 
furnaces used in the soda manufacture. Such furnaces are still 
used in a few mills, and have openings at intervals along the sides, 



170 THE CHEMISTRY OF PAPER-MAKING. 

through which the workman, by means of a long rake, gradually 
moves the burning material from the back towards the front of the 
pan, at which point it is withdrawn after the ignition is complete. 
In this country such furnaces have been almost entirely superseded 
by the Warren rotary furnace, which is shown, with its auxiliary 
apparatus, in Fig. 15. In the drawing, A is the movable fire-box, 
built of fire-brick, either inside an iron shell or held together by 
iron rods and bands. It is mounted on wheels resting upon rails, 
so that it may be easily moved away to give access to the furnace. 
It is either fitted with grate bars for burning coal or wood, or may 
be arranged for gas or oil. 

The furnace itself, Gr, consists of an iron shell lined with fire- 
brick in such a way that the interior is conical, the larger end 
of the cone being toward the fire-box. The furnace is encircled by 
iron rails, which rest upon flanged wheels, as shown at L, and is 
made to revolve by the worm and gear and gear and pinion shown 
at M. The concentrated liquor is admitted to the furnace in a 
regulated stream at J, and gradually works its way forward, being 
exposed to more and more intense heat, until practically all the 
organic matter has been destroyed, and the ignited black ash falls 
out at iV^into an iron cart or conveyer. In order to utilize the waste 
heat from the furnace, a boiler, 0, is set up in such relation to it 
that the hot gases pass under the boiler and then through the 
tubes. By this arrangement a quantity of steam may be generated 
nearly sufficient to carry on the whole process of evaporation up 
to the point where the liquors enter the furnace. A considerable 
proportion of the heat still remaining in the gases is taken up 
by the concentrated liquor in the tank, if, mounted over the 
boiler. 

The throat of the furnace is protected by the water-jacket, K, 
fastened to the back of the fire-box, and projecting a short distance 
into the furnace. This jacket is filled with concentrated liquor 
from the tank H. The colder, and therefore heavier, liquor flows 
in at the bottom of the jacket, through the pipe F, and being ex- 
panded by the heat becomes lighter, and is forced back into the 
tank through the pipe F, as fresh portions of the colder liquor pass 
down F. In this way a constant circulation and rapid heating of 
the liquor in the tank are secured. Those portions of the pipes, F 
and _F, which are fastened to the jacket are of smaller diameter 
than the portions coming from the tank, and project into them 



THE MANUFACTURE OF WOOD FIBRE. 




172 



THE CHEMISTRY OF PAPER-MAKING. 



through stuffing-boxes, so that the fire-box may be moved back 
without breaking the connection. 

We are indebted to Cross and Bevan's " Paper-making " for the 
following cuts and description of the Porion evaporator, which is 
one of the most economical of the large class of evaporators in 
which the liquors are not treated in multiple effect. It is shown 
in sectional elevation and plan in Figs. 16 and 17. It is largely 




Fig. 16. — The Porion Evaporator — Section. 

used on the Continent and also in England and Scotland. It con- 
sists of a large chamber, k, the floor of which is slightly inclined 
from the chimney shaft, and through which the waste heat from 
the furnace, a, passes. 

The liquor to be evaporated is run in at the end nearest the 
chimney from the tank placed above the chamber, c. A number of 
cast-iron fanners, i, dip into the liquor and revolve rapidly, usually 




Fig. 17. 



The Porion Evaporator — Plan. 



at the rate of about 300 revolutions per minute, producing and 
filling the chamber with a very fine spray, thus presenting a very 
large evaporating surface. 

Between the furnace and the evaporator are placed the chambers 
c and f. In c a number of brick walls, d, are so placed that the 
flames from the furnace are intercepted and broken up. The object 
of this is to give time for all the products of combustion to be 
thoroughly burned up, which would not be the case without the 
"small consumer," as these chambers are called. This part is an 



THE MANUFACTURE OF WOOD FIBRE. 173 



addition to the original evaporator, and was devised by Messrs. 
Menzies and Davis. The liquor, after having been concentrated 
in the chamber, k, runs into a trough placed alongside the doors, A, 
and flows into one or the other of the furnace beds, b, where it is 
still further concentrated, and the residue ignited by the flames 
from the fires at a. The draught can be regulated by the damper, g, 
and also by one placed near the shaft, j. The doors, e, in the 
smell-consuming chamber are for the purpose of cleaning out. The 
fanners, i, are worked by a small steam-engine not shown in the 
drawing. The temperature of the gases near the chimney should 
not be higher than about 85° C. By running the fanners at a very 
high speed the temperature of the gases may be still further 
reduced, thus showing the completeness of the evaporation. 

This form of evaporator is open to the objection that the whole 
of the sulphur in the coal employed for the furnaces finds its way 
into the recovered soda. It combines with the alkali to form 
sulphite of soda, part of which is decomposed in the furnace with 
formation of sodium sulphate, sulphide, and other sulphur com- 
pounds. The same objection, of course, applies, though perhaps in 
a less degree, to all systems of evaporation in which the flame is in 
contact with the liquors to be evaporated. 

The Porion evaporator can be erected at very small cost, and 
costs but little for maintenance. It is capable of producing three- 
quarters of a ton of recovered soda per ton of coal with liquors of 
the usual strength. 

A profitable outlet for black-ash waste has recently been opened 
up by a process for its conversion into carbons for arc lights. 

Causticizing. — The strong solution of carbonate of soda pre- 
pared from the mixture of black ash and fresh soda-ash is made 
caustic by treatment with lime in tanks, about 10 feet in diameter 
by 7 feet in height, fitted with agitators and usually with drainer 
bottoms. For every 100 lbs. of carbonate of soda in the liquor 
about 60 lbs. of lime are either thrown directly into the tank or 
else immersed in the liquor in an iron cage fastened to the side of 
the tank. The lime soon slakes, and is carried into the liquor, 
which takes on the appearance of milk of lime. The small quantity 
of lime, which at first goes into solution, reacts with the carbonate 
as shown below — 

CaH 2 2 + Na 2 C0 3 = CaC0 3 + 2 NaOH, 



174 THE CHEMISTRY OF PAPER-MAKING. 

and is precipitated as carbonate of lime ; an equivalent portion of 
fresh lime is immediately dissolved, and the reaction continues 
until either the lime is exhausted or all the soda causticized. In 
order to hasten the reaction the mixture is usually heated to about 
212° F. by a steam-pipe passing through the bottom of the tank. 

The character of the lime used in causticizing is of the first 
importance if good results are to be secured. It should contain as 
little silica as possible, since otherwise there will be a loss through 
the formation of silicate of soda, and the proportion of magnesia 
should be small because of the great insolubility of this base, which 
renders it comparatively ineffective. 

"We give below analyses of two samples of lime, the sample 
marked No. I. being especially good for causticizing, while that- 
marked No. II. is not at all well suited for the purpose : — 

No. I. No. ir. 



Sand and insoluble material . 
Iron and alumina oxides . . 
Lime 


. 0.08 
. 0.89 
. 94.07 


3.16 

2.67 

54.04 


Magnesia 


1.20 


36.80 


Water, carbonic acid, etc. . . 


. 3.76 


3.33 


Totals 


. 100.00 


100.00 



Solvay, in his British patent of 1879, claims that lime slaked in 
a solution of calcium chloride gives a granular hydrate which 
thoroughly causticizes the hot liquors, which are merely run over a 
layer of the material. The hydrate does not lose its form, and can 
therefore be very easily and thoroughly washed. 

G. Lunge has obtained the following results from experiments 
to determine how completely sodium carbonate may be. converted 
into caustic soda by treatment with lime. At the ordinary atmos- 
pheric pressure the experiments gave the following numbers : — 



er cent. Na 2 C0 3 
in liquor. 

2 


Specific gravity before 
causticizing. 

1.022 at 15° C. 


Percentage of soda made caustic 

by treatment. 

I. II. 

99.4 99.3 


5 


1.052 




u 


99.0 


99.2 


10 


1.107 




u 


97.2 


97.4 


12 


1.127 




a 


96.8 


96.2 


14 


1.150 




a 


94.5 


95.4 


16 


1.169 


at 


30° C. 


93.7 


94.0 


20 


1.215 




a 


90.7 


91.0 



THE MANUFACTURE OF WOOD FIBRE. 175 

Corresponding experiments, conducted under pressure, at a tem- 
perature of 148° to 153° C, gave — 



Per cent. Na,C0 3 
in liquor'. 


Specific gravity before 
causticizing. 


Percentage of soda made caustic 

by treatment. 

I. II. 


10 


1.107 at 15° C. 


97.06 




97.50 


12 


1.127 


96.35 




96.80 


14 


1.150 " 


95.60 




96.60 


16 


1.169 at 30° C. 


95.40 




94.80 


20 


1.215 


91.66 




91.61 



From which it appears that there is no appreciable gain when the 
operation is performed under pressure, and that, as was already 
held, the best results are obtained from the weaker liquors. 

Mills which are located upon small streams sometimes experi- 
ence considerable difficulty in disposing of the waste-lime mud 
from the causticizing tanks. This difficulty has been met by the 
lime reclaimer invented by Mr. George W. Hammond, and shown 
in section in Fig. 18. The lime-mud is fed at G- into the flue, F, 
which is 24 feet long, and through which the mud is slowly 
carried forward by means of an Archimedes screw. The nearly 
dry mud is then discharged into the rotary furnace, (7, which 
is driven by gears as shown at H. The material coming 
from this furnace is guided by the connecting flue, D, into the 
second furnace, C, which discharges the recovered lime through 
the opening B, in front of the fire-box, A. In order to drive off 
all the water and set free the carbonic acid, a very high tempera- 
ture and a considerable period of time are necessary, so that very 
long furnaces are required if the process is to be continuous and 
the output at all large. In the apparatus erected by Mr. Ham- 
mond each furnace is 40 feet long, and the capacity is about five 
tons of recovered lime per day. 

The Hewitt and Mond causticizing process, or the ferric oxide 
process, as it is called, has been lately introduced in England, and 
depends upon the fact that when a mixture of ferric oxide and 
carbonate of soda is strongly ignited the iron acts as an acid to 
displace the carbonic acid with the formation of sodium ferrate 
which is so unstable that washing with hot water removes the 
caustic soda, leaving the ferric oxide in condition to be used again. 
In practice, three parts of ferric oxide, originally in the form of 
" Blue Billy," which is the cinder from pyrites burning, are used 
to every one part of soda-ash. 



176 



THE CHEMISTRY OF PAPER-MAKING. 




THE MANUFACTURE OF WOOD FIBRE. 177 

An analysis by ourselves of the " Blue Billy " as used gave 
figures as below : — 

Per cent. 

Moisture (loss on ignition) 7.50 

Sesquioxide of iron (Fe 2 3 ) 65.49 

Alumina (A1 2 3 ) 0.89 

Sand and silica (insoluble in acid) .... 24.72 

Oxides of lead and copper traces. 

A rotary furnace, usually 18 feet long and 10 feet in diameter, 
is charged with two tons of the mixture of this material and soda- 
ash, and turned at the rate of one and a quarter revolutions per 
minute in order to prevent fluxing. About 1400° F. seems to be 
the temperature necessary for the reaction, and most of the time 
is consumed in bringing the charge to that heat. The reaction 
proceeds rapidly after it is once begun. About five charges can be 
worked in such a furnace in twenty-four hours, with the consump- 
tion of seven long- tons of coal. The ferrate of soda is removed to 
tanks fitted with drainer bottoms, and is there leached with hot 
water in the same systematic way in which black ash is treated. 
In order to settle out all of the oxide of iron it is necessary to 
allow the liquors to stand about four days. It is possible by this 
process to make liquors of a strength of 80° T. 

The percentage of soda recovered varies, of course, within con- 
siderable limits, according to the efficiency of the apparatus and 
the care with which the different stages of the process are con- 
trolled. Some mills fail to recover more than 60 per cent., while 
others, in exceptional months, show figures as high as 95 per cent. 
The average recovery is probably from 75 to 78 per cent., but in 
the best practice the amount reclaimed runs from 85 to 90 per cent. 
The percentage of recovery at the Willsborough Mill of the New 
York and Pennsylvania Company for 1891 is given to us as 89.11 
per cent. 

The main sources of loss in recovery are : — 

Imperfect washing of the pulp. 

Volatilization of the carbonate in the furnace, or, which amounts 

to the same thing, its escape as dust carried into the chimney 

mechanically by the furnace gases. 
Imperfect leaching of the black ash. 
Retention of soda in the lime-mud after causticizing. 



178 THE CHEMISTRY OF PAPER-MAKING. 

The greatest loss is likely to occur in washing the pulp, and 
this can only be kept down by conducting the operation in the 
most systematic and thorough manner possible. With great care 
the losses in causticizing and in leaching the black ash need not 
amount together to more than 1 per cent. An appreciable quan- 
tity of soda is undoubtedly lost up the chimney, and it is difficult 
to either check this loss or accurately estimate its amount. This 
item is a sort of residuary legatee, to which is credited the balance 
of loss which cannot properly be charged to the other accounts. In 
running a soda pulp mill the most careful superintendence is likely 
to be thwarted unless it is supplemented by careful and frequent 
chemical tests at every stage of the process. Such tests are fully 
described in the chapter on Chemical Analysis. 

The following figures, which are taken from mill records, are of 
interest as showing the minimum to which the losses at the points 
indicated have been brought in practice : — 

In washing 2 to 3 per cent. 

Causticizing and leaching black 

ash, together 0.75 to 1 " 

Up chimney 2 to 3 " 

The Sulphate Process. — This interesting modification of the 
soda process was introduced by Dahl, at Danzig, about 1883. In 
it sulphate of soda is made to replace, in large part, the more 
expensive carbonate. According to Schubert, the liquor is in the 
first instance made up from a mixture of three parts sulphate of 
soda and one part caustic. After cooking the wood, the liquor is 
evaporated and calcined, and yields a reddish brown ash, which has 
about this composition : — 

Per cent. 

Sodium sulphate 16 

" carbonate 50 

" hydrate 20 

" sulphide 10 

Various materials 4 

100 

The composition of the ash varies, however, according to the 
treatment, but the solvent power of the liquor made therefrom is 
not especially affected. The loss in recovery is 10 to 20 per cent. 
New liquor is then made by adding sufficient sulphate of soda to 



THE SULPHITE PROCESS. 179 



replace the salts lost, and heating the whole with 20 to 25 per 
cent, of lime. In regular operation the boiling liquors generally 
contain a mixture of salts composed of about — 

37 parts sodium sulphate. 

8 parts sodium carbonate. 
24 parts sodium hydrate. 

3 parts sodium sulphide. 

The strength of the lyes ranges from 6 to 14° Be. Iron boilers 
are used, and the cooking, which requires from thirty to forty 
hours, is conducted at a pressure of 75 to 150 lbs. The main objec- 
tion to the process is found in the stench which necessarily arises 
from the sulphides present in the liquors. Sulphate pulp is of 
excellent quality, soft and strong. That found in this market is 
made from coniferous trees, probably spruce and fir. Three grades 
are common — the unbleached, half-bleached, and bleached. 



THE SULPHITE PROCESS. 

The first patent involving the use of sulphurous acid in reducing 
wood to pulp was that numbered 70,485, and issued Nov. 5, 1867, 
to Benjamin C. Tilghman, then of Philadelphia, and a chemist to 
whom many branches of technology are much indebted. A sup- 
plementary patent, Number 92,229, covering the treatment of 
fibrous materials at the ordinary pressure, was issued to the same 
inventor in 1869. These patents form the basis of all the various 
modifications of the process in operation at the present time. 
The numerous subsequent patents to other inventors cover merely 
improvements in apparatus and details of treatment. 

Tilghman states that his invention consists in a process of treat- 
ing vegetable substances which contain fibres with a solution of 
sulphurous acid in water, heated in a close vessel, under a pressure 
sufficient to retain the acid gas until the intercellular incrusting 
or cementing matter existing between the fibres is dissolved, either 
partially or wholly, as may be desired, and a fibrous product is 
obtained suitable for the manufacture of paper pulp or of fibres, or 
for other uses, according to the nature of the material employed. 

The following abstract of Tilghman's original patent will serve 
to indicate how carefully and thoroughly he had worked his 



180 THE CHEMISTRY OF PAPER-MAKING. 

process out in the experimental way, and how clearly he perceived 
all its possibilities. His difficulties, which he later found too seri- 
ous for him to overcome, were evidently confined almost entirely 
to the engineering side of the process. 

The specification calls for a strong iron vessel of convenient 
size and shape, lined with lead, and provided with a steam jacket, 
and with the necessary pipes, cocks, and manholes for filling and 
emptying the charge ; and with gauges, safety valves, and ther- 
mometers to indicate height of liquid, pressure, and temperature. 
This vessel is about two-thirds filled with chips, hemlock or poplar 
being specified. A solution of sulphurous acid in water, of specific 
gravity 1.025 to 1.035, in which a quantity of sulphite of lime 
has been dissolved, sufficient to raise its density to about 1.07 to 
1.08, is run in until the amount is sufficient to keep the wood 
constantly covered by the liquid during treatment. The boiling 
is conducted for about eight hours, at 260° F., when fresh water is 
forced in at the top of the digester to wash out the acid solution. 
If the pulp, upon examination, proved, as was undoubtedly the 
case, to be imperfectly separated, it was to be again treated with 
afresh charge of sulphurous acid and sulphite at a temperature 
from 260 to 280° F., for three to five hours, as might be necessary. 
The patentee speaks of the quantity of sulphite of lime deposited 
during the boiling, and points out that it may be re-used together 
with the sulphurous acid gas which may be driven off from the 
waste liquor. He states that the stronger the acid solution, the 
more rapid is the action at a given temperature. Also, the higher 
the temperature, the more rapid is the action with a given density 
of solution ; with weak acid and comparatively low temperature, 
he says, foreshadowing the Mitscherlich process, the effect can 
be produced by continuing the digestion a sufficiently long time. 
Sulphurous acid in water at the requisite temperature appears to 
be the efficient agent in dissolving the intercellular or cementing 
matter of the vegetable fibrous substance, and where the color of 
the product is of no consequence, the operation may be performed 
with the sulphurous acid alone, without the addition of sulphite. 
In this case a reddish brown color is given to the resulting fibrous 
product, and the acid solution will be found to contain a quantity 
of free sulphuric acid, which has been formed during the operation 
by the oxidation of a portion of the sulphurous acid. This is 
directly in line with the Pictet process. The presence of a sul- 



THE SULPHITE PROCESS. 181 



phite in the acid solution prevents this reddening effect, and in 
case of many substances a considerable bleaching of the fibrous 
product takes place. 

Tilghman's idea at this time was that the office of the sulphite 
was to present a base with which the sulphuric acid could combine 
as fast as formed, and he therefore naturally supposed that many 
other of the salts of the weaker acids, such, for example, as the 
acetates, could replace the sulphites more or less perfectly, in 
the presence of sulphurous acid. Subsequent experiments and a 
more complete knowledge of the chemical process have shown 
this to be incorrect, since the sulphite not only neutralizes the 
free sulphuric acid, but has also a very important influence in 
the process depending upon its power of forming double com- 
pounds with certain of the derivatives of the wood. 

On account of their historical interest and important bearing on 
the process, we give below in full the claims of Tilghman's first 
patent : — 

The process of treating vegetable substances which contain fibres with a 
solution of sulphurous acid in water, either with or without the addition of 
sulphites or other salts of equivalent chemical properties as above explained, 
heated in a close vessel, underpressure, to a temperature sufficient to cause it to 
dissolve the intercellular incrusting or cementing constituents of said vegetable 
substances, so as to leave the undissolved produce in a fibrous state, suitable for 
the manufacture of paper, paper-pulp, cellulose, or fibres, or for other purposes, 
according to the nature of the material employed. 

I also claim as new articles of manufacture the two products obtained by- 
treating vegetable substances which contain fibres with a solution of sulphurous 
acid in water, either with or without the addition of sulphites or other salts 
of equivalent chemical properties as above explained, heated in a close vessel, 
under pressure, to a temperature sufficient to cause it to dissolve the intercellular 
or incrusting constituents of said vegetable substances, one of said products 
being soluble in water, and containing the elements of the starchy, gummy, and 
saline constituents of the plants, and the other product being an insoluble 
fibrous materia], applicable to the manufacture of paper, cellulose, or fibres, or 
to other purposes, according to the nature of the material employed. 

I also claim the use and application, in the manufacture of paper, paper-pulp, 
cellulose, and fibres, of the fibrous material produced by treating vegetable 
substances which contain fibres with a solution of sulphurous acid in water, 
either with or without the addition of sulphites or other salts of equivalent 
chemical properties as'above explained, heated in a close vessel, under pressure, 
to a temperature sufficient to cause it to dissolve the incrusting or intercellular 
constituents of said vegetable substances. 

I also claim the use and application of sulphites or other salts of equivalent 



182 THE CHEMISTRY OF PAPER-MAKING. 

chemical properties as above explained, in combination with a solution 01 
sulphurous acid in water, as an agent in treating vegetable substances which 
contain fibres, when heated therewith in a close vessel, under pressure, to a 
temperature sufficient to cause said acid solution to dissolve the intercellular or 
incrusting constituents of said vegetable substances. 

I also claim the recovery and re-use of sulphurous acid and sulphite from the 
acid liquids which have been digested on the vegetable fibrous substances, by- 
boiling said liquids or neutralizing them with hydrate of lime. 

Theory of the Sulphite Process. — It is well known that 
many of the more complex members of the carbohydrate group, to 
which cellulose belongs, undergo more or less pronounced change 
upon being boiled with water, especially if the boiling is conducted 
at the higher temperatures obtained under pressure in a closed 
vessel. Sugar, which is the typical member of the group, becomes 
inverted ; that is, the sugar combines to a limited extent with the 
elements of water, and the more complex molecule thus formed 
breaks down into the two simpler ones of dextrose and levulose. 
Such an action in which, as a result of taking up the elements of 
water, a molecule is broken down, is called a hydrolytic action, and 
the decomposition itself is called hydrolysis. Similar changes, as 
before stated, are brought about through the action of water alone 
upon the more complex carbohydrates, such as cellulose and its 
incrusting matters, if not upon all the members of the group ; but 
these changes proceed far more rapidly and completely in the 
presence of dilute acids. Cellulose itself is comparatively stable 
under these conditions, unless the temperature is considerably 
raised, but Tauss and others have shown that it is by no means un- 
acted upon. Lignin, probably from its greater complexity, is broken 
down with considerable rapidity at temperatures not much higher 
than that of the boiling-point of water. The products of the decom- 
position are largely organic acids, and the direction of the decom- 
position is toward the production of these acids, but among the 
earlier products there undoubtedly occur a considerable proportion 
of substances having, at least, the general character of the alde- 
hydes. When the ordinary mineral acids, as sulphuric or hydro- 
chloric acid, act in the dilute form, and at moderately high tempera- 
tures, upon wood, the decomposition products rapidly accumulate 
in the liquor, and undergo further secondary decompositions, the 
course of which tends toward the production of insoluble, dark- 
colored, and tarry matters. It is obviously impossible under these 



THE SULPHITE PROCESS. 183 

conditions to look for the production of cellulose in any condition 
of purity. 

The reaction undoubtedly takes a somewhat similar course when 
sulphurous acid without any base is used ; indeed, this acid is well 
known to have a decomposing action upon many groups of organic 
compounds. As a reducing agent, using the word in its chemical 
sense, the acid retards and limits the secondary changes, but it does 
not altogether prevent them. The brown color of pulp obtained 
by the Pictet process is due in part to the products of the changes 
set up by the sulphurous acid, as well as to those which are induced 
by the sulphuric acid formed during this process. This is shown 
by the fact that the addition to the liquor of the very small amount 
of soda required to neutralize this sulphuric acid does not prevent 
the browning of the pulp. 

The primary action of a bisulphite liquor in resolving wood 
proceeds upon the same lines as that of a solution of sulphurous 
acid, but the presence of the base in this combination materially 
modifies the subsequent course of the reactions. The bisulphites 
possess the remarkable property of forming, with the aldehydic 
products of the first stage of the decomposition, true double com- 
pounds which are soluble and comparatively stable. Compounds 
of this class have been found in the waste liquors. It is charac- 
teristic of the aldehydes that they pass by oxidation into organic 
acids, and in spite of the presence of sulphurous acid, which tends 
to prevent oxidation, there is some formation of these acids. 
Once formed, they displace the sulphurous acid from an equiva- 
lent portion of the base, and form soluble organic salts. By these 
two actions the bisulphites take up the products of the resolution 
of the wood, and prevent for the most part the extreme degrada- 
tion of the products which is characteristic of the water treatment 
or of the soda process. The combination of the acid products 
with the base is shown by the steady rise in the gas pressure 
observed during the last part of a sulphite cook, and which is 
avoided by blowing off. It is also shown by the composition of 
the waste liquors. A. Ihl finds that the resinous matter obtained 
by evaporating these liquors consists mainly of the calcium salts 
of acids similar to Arabic acid, and that these acids, as indicated 
above, decompose carbonates, sulphites, and sulphides. 

An incidental advantage of considerable importance is obtained 
by the use of sulphurous acid in connection with a base, and is 



184 THE CHEMISTRY OF PAPER-MAKING. 

due to the power of this acid to form with various coloring-matters 
compounds which are themselves colorless. The practical effect 
of this latter action is the production of a fibre which may be at 
first of a color as good as that of well-bleached pulp, although, as 
in case of all sulphurous acid bleaching, this high color does not 
persist for any considerable length of time. 

Although all the bisulphites act in general in the manner 
specified above, the character of the liquor is modified in several 
important particulars, according as one base or another is in 
combination with the acid. Bisulphite of lime is a very unstable 
salt which upon being merely heated decomposes ; one-half of the 
acid being set free. The resulting monosulphite is practically 
insoluble, so that when this decomposition occurs in the boiler, 
this latter salt is precipitated throughout the pulp, from which it 
is difficult to remove it by washing. Where lime liquor is used, 
there is therefore more gas pressure in the digester, and the 
resulting pulp is comparatively harsh, hard, and transparent. It 
is also more difficult to make a straight lime liquor of high test 
than it is to prepare similar liquors from magnesia or soda, but 
on account of the insolubility of sulphate of lime the former 
liquors never contain more than three-tenths per cent, of sulphuric 
acid, while soda or magnesia liquors may contain an indefinite 
amount. In the case of lime liquors, any excess of sulphate over 
the amount given is precipitated and may be settled out. 

Bisulphite of magnesia is somewhat more stable than the corre- 
sponding lime salt, and its action on the incrusting matter is 
milder, but even more effectual. The sulphates or monosulphites 
which may be present in magnesia liquors remain in solution, and 
are easily washed out from the pulp. The resulting product is 
much softer and whiter than any which is ordinarily made Avith 
lime without some subsequent treatment. These desirable qualities 
of magnesia are possessed in a still higher degree by soda. Sodium 
bisulphite is so permanent that it may be easily obtained and 
preserved in the crystalline form. The gas has so strong an 
affinity for the base that liquors of 35° B6 may be made without 
difficulty. Both the sulphite and sulphate of soda are very soluble, 
and there is therefore no precipitation either in the liquor appa- 
ratus or in the digester. Pulp made with soda liquor is white 
and soft, and almost entirely free from the last portions of 
incrustino' matter. 



THE SULPHITE PROCESS. 185 

It has been held in some quarters that sulphuric acid in con- 
siderable amount is formed in the digester during boiling, but 
numerous experiments by ourselves and others show that in reality 
this oxidation of the sulphurous acid is very slight ; it is obviously 
so when we consider that making no allowance for the chips and 
liquor in the digester, but supposing the whole interior to be 
rilled with air at the ordinary temperature and pressure, the total 
amount of oxygen contained therein only amounts to 22 lbs. in 
a digester of a capacity of 1200 cubic feet, a quantity so small 
when compared to the weight of sulphurous acid in the liquor that 
it may be disregarded. An additional proof is found in the Pictet- 
Brelaz process in which it is possible to recover as sulphurous acid 
95 per cent, of all the gas originally present in the liquor. 

History. — Tilghman is said to have spent about $40,000 in ex- 
periments at a mill at Manayunk, Pa. He boiled in long ten-inch 
cylinders, lead lined. Although excellent fibre was obtained, the 
engineering difficulties proved so serious that the experiments 
were finally abandoned. 

After the failure of Tilghman to put his process upon a com- 
mercial footing it was taken up by Fry and Ekman at Bergvik, 
Sweden, about 1870, after a course of experiments in which nitric 
and various acids and water alone had been tried as resolving 
agents. In 1872 the present Ekman process, using a solution of 
bisulphite of magnesia, was so far developed that these gentlemen 
had a three-ton mill running on a commercial basis with eight 
small jacketed digesters. The process was worked secretly 
until about 1879. It was introduced into England in a small 
way at Ilford Mills, near London, after which, in 1881, the pro- 
prietors of the patent erected a large mill at Northneet, also near 
London. 

Although in no way essential to his process, Ekman has always 
favored the preparation of this solution in towers. Those first used 
at Bergvik were 5 feet in diameter, 14 feet high, and filled above 
the false bottom with calcined magnesia. They carried at the 
top sprinklers for distributing and regulating the flow of water. 

The next to assist in the development of the process was 
Mitscherlich, then professor of chemistry at Miinden, and a son of 
the celebrated discoverer of the law of isomerism. He began his 
experiments at the mill of F. Keferstein, Ermsleben, near the Hartz 
Mountains, about 1876, and later went to Thocle's Mill, near 



186 THE CHEMISTRY OF PAPER-MAKING. 

Dresden. He did not get started on a commercial scale until about 
1880 or 1881. 

On the 11th of October, 1883, Moritz Behrend, the lessee of 
Prince Bismarck's mill at Coeslin, disputed the validity of the 
Mitscherlich patents. He relied chiefly upon the Tilghman British 
patent, No. 2924, dated Nov. 9, 1866. After a very long trial 
and examination of technical experts, the German Board of Patents 
concluded that the Mitscherlich process did not differ from that 
of Tilghman sufficiently to entitle it to protection. 

Francke, in Gothenburg, Sweden, began his experiments about 
1879, his attention, it is said, being turned in this direction 
through the introduction to him of one of Ekman and Fry's 
chemists. He began work in a commercial way about 1882. His 
process has so far secured no foothold in this country, and presents 
few points of interest. The liquor is prepared in towers, and the 
digester is a horizontal rotary cylinder, lead lined. The lining is 
held in place by rings of various construction. 

The Partington process, which was acquired by the American 
Sulphite Pulp Company, about 1884, was one of the first to be intro- 
duced here. The liquor plant shows a radical departure from 
those previously used, and will be described in detail under 
Liquor Making. The digesters are spherical rotaries. The various 
steps taken by Partington in the development of his system for 
lining these digesters comprise one of the most interesting studies 
in engineering which the process has shown. They will be dis- 
cussed at some length in the section given to digester linings. 

McDougall was for some time associated with Partington, and 
his plant in 1887 differed little from the last described, except in 
the method adopted for lining digesters. 

Various other manufacturers in different parts of Europe started 
almost contemporaneously with these workers. Graham in Eng- 
land, who had been chemist to Ekman and Fry, applied to digester 
linings a method by which the lead was caused to adhere uniformly 
over the surface of the iron shell, and worked out a special modi- 
fication of the Ekman process, which consisted in re-enforcing the 
strength of the boiling liquor during cooking by fresh charges of 
gas. Graham's process has not come into practical use, but the 
digester has been adopted by Ekman, and by some mills in this 
country. Flodqvist for a time exploited the process in Avhich a 
liquor containing both bisulphite and phosphate of lime was used, 



THE SULPHITE PROCESS. 187 

the liquet being made in a series of towers, some of which were 
packed with limestone and others with the bones which furnished 
the supply of phosphate. Kellner in Austria, who was at that time 
associated with Baron Ritter, and who is one of the most skillful 
chemical engineers who has turned his attention in this direction, 
had taken out, in 1885, several patents covering a special process, 
liquor apparatus and digester, which were then in successful 
operation. 

The difficulties occasioned by the use of an acid sulphite had, as 
early as 1880, led Cross to bring out a process employing an 
alkaline solution of sulphite of soda in iron digesters, unlined. 
This reagent has no effect on the iron, but its use necessitates the 
carrying of considerably higher pressures than where the bisulphite 
is used, the bleaching action of the sulphurous acid is much re- 
stricted, and the cost of chemicals much increased. There is, 
moreover, according to our own experiments, a precipitation under 
these conditions of free sulphur throughout the pulp. The Pictet- 
Brelaz process, on the other hand, which was brought out in 1883, 
goes to the other extreme, and instead of increasing the amount 
of base as Cross had done, does away with it altogether, the wood 
being boiled at a temperature never exceeding 105° C, in a solu- 
tion carrying from 7 to 8 per cent, sulphurous acid. 

The first American paper-maker to introduce the process upon 
a commercial scale in this country was Charles S. Wheelwright, 
then of Providence, R.I. The Ekman process was the modifica- 
tion selected, after a visit, in 1882, to the small mill in which it 
was in operation at Bergvik, Sweden. Although the process as 
there shown was evidently very imperfect on the mechanical side, 
the high grade of the product encouraged Mr. Wheelwright and 
his associates to erect on a large scale the now historical plant of 
the Richmond Paper Company. 

Pulp of the highest quality was made almost from the start ; 
but the mechanical difficulties of working the process on a large 
scale proved so serious that in spite of his untiring energy, Mr. 
Wheelwright soon found himself in almost the position of the 
original inventor, Tilghman. 

The towers filled with calcined magnesia, as was the case at 
Bergvik, gave endless trouble from the difficulty of regulating the 
flow of water, from the great tendency of the magnesia to soften 
up and form mud, and finally, from the liability, when the water 



188 THE CHEMISTRY OF PAPER-MAKING. 

supply was temporarily stopped, of the whole mass to cake and 
bind together through the formation of monosulphite of magnesia. 
These defects in the apparatus frequently made it impossible to 
secure regular or free draft up through the tower, the output of 
liquor was small, and both its quantity and composition were 
irregular. After trials on a large scale, with many different forms 
of apparatus, those difficulties were entirely overcome by the 
adoption of the apparatus suggested by Catlin. Obstacles equally 
serious were encountered in working the digesters, as the engi- 
neering problems presented were such that no precedents could be 
found for guidance. Various forms of digester were designed in 
succession by Mr. Wheelwright to such good effect that the cost 
of repairs on linings were in about three years reduced from over 
$10.00 to about $1.50 per ton of product. Throughout all this 
period of difficulty the product of the mill was equal, if not 
superior, to any which has since been produced here or abroad. 

Except in a few instances which will be noted, the subsequent 
development of the process in this country has proceeded upon 
the lines laid down in Europe, although numerous forms of 
digesters and liquor apparatus have appeared. Two new systems, 
those of Schenck and Crocker, have been developed commercially, 
and the former has been widely introduced. The main novelty 
of the Schenck process is found in the digester, which is built up in 
three-feet sections cast from a special bronze. His liquor apparatus 
differs slightly from that of Partington, and the general method 
of procedure in the process itself is much the same. The Crocker 
process differs from all those before mentioned in that it employs 
a solution of bisulphite of soda prepared by double decomposition 
by treating bisulphite of lime solution with sulphate of soda. 

Preparing- Wood. — Owing to the great solvent power of the 
alkali in the soda process, comparatively little pains are necessary 
in the preparation of the wood. In the sulphite process, however, 
all portions of bark and knots which go into the digester are only 
slightly acted upon by the liquor, and are liable to cause dirt in 
the pulp. It is a prime necessity, therefore, that all bark should 
be carefully removed either by draw-shaves or by a barker. This 
applies as well to the light-colored inner bark as to the outer bark. 
Wherever, on account of an old wound in the tree, the bark is 
turned inward, these portions are best cut out by hand, since the 
use of the barker involves in these cases an unnecessary loss of 



THE SULPHITE PROCESS. 189 



sound wood. All portions of wood, also, that are decayed or 
badly stained, must be removed. A difference of opinion exists 
as to the proper method of handling knots. In some mills it is 
the practice to remove all knots by boring ; but this seems to us 
objectionable, since it not only involves considerable labor, but is 
liable to cause fine dirt in the pulp by splitting up portions of the 
knot into small fragments which will get through the screens. 
As the sound knots are hardly softened at all by the liquor, the 
preferable plan, in our opinion, is to make no attempt to remove 
them until after the wood has been brought to pulp. They are 
thus left in pieces of such large size that they are readily taken 
out upon the screen, and all danger of fine dirt from this cause is 
avoided. Rotten knots break up in the cooking and subsequent 
operations, and should be cut out. Where labor is sufficiently 
cheap to admit of its being done, it is well to have the wood 
coining from the chipper thrown Upon an endless belt, by the 
sides of which boys or girls ma} r be stationed to pick out all knots 
and unsound chips. This is the universal practice in sulphite 
mills abroad. Some of these foreign mills go to the further extents 
of sorting their chips to size. We have failed to discover that 
this offers any advantages to compensate for the increased cost. 

In many mills the wood, after leaving the chipper, is passed 
between crushing rolls, one running at twice the speed of the 
other, and both covered with coarse, pyramidal teeth. A toothed 
scraper under the bottom roll acts as a doctor. The advantage of 
crushing is that it permits more rapid absorption of the liquor, so 
that cooks can be made more quickly and with less danger of 
leaving any of the chips with a hard, red, central portion. The 
knots, however, are likely to be broken up, and the quantity of 
wood which can be cooked at one time is somewhat diminished. 

All the chips cooked at one time should be of a single kind of 
wood, and as nearly as possible in the same condition as regards 
age and moisture. The treatment necessarily varies for different 
woods, and even for the same wood when dry or green. Where 
it can be done, it is advantageous to keep the wood in water for 
some time before chipping, as it is thus all brought to the same 
state of moisture. Green wood is more easily reduced by the 
sulphite process than wood which has been seasoned. 

Although chips are used in some instances where mills are 
working the Mitscherlich process, the more general practice is to 



190 THE CHEMISTRY OF PAPER-MAKING. 



cut the log into discs 1\ inches thick by gang-saws. It is claimed 
that in this way, where the slow method of packing the digester 
by hand is followed, more wood can be handled at a boiling, and 
better circulation secured, than where chips are used. 

The use of chips, however, involves less time and labor and the 
yield per cord is greater, as at least 10 per cent, of the wood must 
be lost as sawdust when discs are used. Where the chips are 
properly handled, the fibre, for all practical purposes, should not 
have its length or strength impaired. 

Spruce is the wood most commonly used in this country for 
making sulphite pulp, but much of the foreign fibre is made from 
the Swedish fir. Any of the coniferous woods which are not too 
resinous to yield easily to treatment may be used in place of 
spruce ; but as each wood has its own peculiarities which call for 
differences in treatment, it is best cooked separately and unmixed 
with other woods. 

Iaquor-Making\ — The preparation of the solution used in the 
sulphite process depends upon, or is influenced by, several general 
facts which it is well to recall here. When sulphur is heated in 
the air, it first melts to an amber-colored liquid at 115° C. ; as the 
heating is continued, the melted sulphur gradually darkens in color 
and becomes very thick and tenacious ; at a still higher tempera- 
ture it partially regains its fluidity; and at about 300° C. begins 
to vaporize. If this dark, reddish brown vapor is allowed to cool, 
the sulphur is deposited either in the powdery form as flowers of 
sulphur, or as a liquid, according to conditions of temperature. 
Sulphur burns in the air with a blue flame tipped with white, 
forming sulphurous acid gas, S0 2 . This gas is very soluble in 
water, one volume of water at zero dissolving seventy-nine volumes 
of the gas. The facility with which the gas is absorbed varies 
greatly with the temperature and pressure, diminishing rapidly as 
the temperature rises ; while at a given temperature the amount 
absorbed varies directly as the pressure. The moist gas has a 
very strong affinity for oxygen, with which, in the presence of 
water, it combines to form sulphuric acid, H,S0 4 . Since only 
about one-fifth of the volume of air is oxygen, and since for every 
volume of oxygen consumed in the first instance by the burning- 
sulphur there is formed only an equal volume of sulphurous acid, 
the strongest gas which can possibly be made in practice can only 
contain about 20 per cent. S0 2 . As a matter of fact, the content 



THE SULPHITE PROCESS. 191 

of S0 2 rarely reaches 10 per cent. The gas going into the absorp- 
tion apparatus is therefore so largely diluted with the waste nitro- 
gen from the air and the unconsumed oxygen, that the absorption 
proceeds at a much slower rate than would be the case could the 
pure gas be obtained, and there is even a considerable tendency 
for the waste gases to sweep the free sulphurous acid out of a 
strong liquor through or over which they pass. 

The different forms of apparatus in which the liquor is prepared 
may be divided for our present purpose into two classes : those in 
which the gas is brought in contact with water containing the 
base in solution or suspension, and those in which the gas and 
water come in contact with the carbonate of the base, which, 
instead of being minutely subdivided, is present in lumps of con- 
siderable size. In the former case the gas is first dissolved by the 
water forming the true sulphurous acid, H 2 S0 3 . This acid immedi- 
ately reacts with the base to form the monosulphite. If the base 
is soda, the sulphite remains in solution, and the same is true to a 
considerable extent of sulphite of magnesia. Sulphite of lime, 
however, is very insoluble, one part of the salt requiring for its 
solutio.n 800 parts of water, so that when milk of lime is used, the 
sulphite is precipitated in the crystalline form as fast as it is made. 
The formation of monosulphite goes on until all the lime is pre- 
cipitated. As the absorption of gas continues, the monosulphite 
gradually takes up an additional equivalent of the acid, forming the 
bisulphite, which is readily soluble. Unless the quantity of base is 
excessive, nearly the whole of the lime is thus brought into solu- 
tion. Owing to the great tendency of sulphurous acid to oxidize 
with the formation of sulphuric acid, and the difficulty of properly 
regulating the supply of air, there is always formed, in practice, 
with the bisulphite, more or less sulphate which, being insoluble, 
remains in the liquor as a white precipitate, which may be readily 
distinguished from the still more insoluble monosulphite by the 
yellow color and more granular appearance of the latter. In 
the second type of absorption apparatus the gas is absorbed by 
the water as before, and the solution thus formed reacts upon the 
carbonate which is present in the form of limestone or dolomite, 
forming sulphite of lime and setting free carbonic acid, as shown 
in the reaction — 

H 2 S0 3 + CaC0 3 = CaS0 3 + H.O + C0 2 . 



192 



THE CHEMISTRY OF PAPER-MAKING. 



After a time the surface of the limestone becomes more or less 
crusted with the sulphite, and as more gas is absorbed this crust is 
brought into solution as bisulphite. There is, however, in such 
forms of apparatus a tendency for both these reactions to proceed 
simultaneously when there is a free supply of gas ; that is, fresh 
portions of limestone are being changed to monosulphite, while at 
the same time portions of monosulphite are being dissolved by the 
acid solution. The formation of sulphate of lime proceeds here as 
in the former case, but considerable portions of it adhere to the 
limestone as a crust. 

The absorption of gas takes place only at the surfaces of contact 
between gas and liquor, so that, other things being equal, the most 
efficient apparatus is the one in which the liquid presents the great- 
est amount of surface to the action of the gas. 

Sulphur Burning 1 . — Sulphur is found in the market in three 
grades, known as firsts, seconds, and thirds, the only differences in 
the three grades being those of color and in the amount of dirt and 
ash present. In seconds the ash rarely exceeds |- per cent. A 
form of sulphur known as Chance recovered sulphur has been 
lately put upon the market, and is for all practical purposes 
chemically pure. The following are analyses made in our labora- 
tory of commercial sulphur : — 





Seconds. 


Chance recov- 
ered sulphur. 


Moisture 


0.01 

0.06 
99.93 


0.20 

■ 0.76 
99.04 


0.06 

99.82 




Foreign matter, insoluble 
disulphide .... 


in carbon 


0.016 


Sulphur 


99.984 


Ash 




0.37 


0.12 


0.012 



Thirds usually contain about 1 per cent, of foreign matter, but the 
proportion runs in rare cases as high as 3 per cent. 

Seconds and thirds are most commonly used in making sulphite 
liquors ; but in many Eastern mills recovered sulphur is now being 
used, on account of its greater purity and the fact that because it 
is shipped in bags it can be handled more easily than the Sicilian 
sulphur, which comes in bulk. In the West considerable Utah 
sulphur is now being used. 



THE SULPHITE PROCESS. 



193 



The dimensions and construction of sulphur furnaces show- 
great variations in different mills. The best styles conform to 
the following requirements : They should be as nearly air tight 
as it is possible to make them, except at those points where pro- 
vision is made for admitting and regulating the supply of air ; the 
pan should be perfectly level, and of such size that not more 
than 2|- lbs. of sulphur need be burned per square foot of pan 
surface per hour ; the pan should be so supported by foundations 
as to leave an air-space under its entire length, in order to keep 
it as cool as possible ; and the entire furnace should be so con- 
structed as to avoid as far as may be the danger of overheating. 




Pig. 19. — Retort Sulphur Furnace. 



The retort style of furnace shown in Fig. 19 is in very common 
use ; and where pains are taken to have the door fit closely, this 
furnace is perhaps as satisfactory as any for plants of moderate 
size. The body of the furnace is in one piece, and is made of 
cast iron, an inch, or better, an inch and a half in thickness. It 
is about 8 feet 6 inches long, and 2 feet 6 inches wide, on the 
outside ; the inside perpendicular being 18 inches. The 8-inch 
pipe by which the gases leave the furnace is either bolted to the 
back of the furnace, as high as possible above the pan, or else to 
the top of the arch near that end. A second casting with guides 
and bearings for the door is bolted to the perpendicular face which 
forms the open end of the retort. The retorts are supported by 
brick foundations which, when properly built, contain an air-space 
extending along the bottom or pan of the furnace. The retorts 



194 



THE CHEMISTBY OF PAPER-MAKING. 



are sometimes surrounded by a water-jacket ; and in other eases a 
shower of water is delivered from a sprinkler pipe upon the top 
of the furnace. 

Similar furnaces, but with doors which can be closed air-tight, 
are used for burning sulphur under pressure, as shown in Fig. 33. 

Ekman introduced a furnace built of |-inch boiler iron, riveted 
together, and caulked air-tight. The dimensions of the pan are 
about 2 feet 3 inches by 7 feet, and the height of the furnace 
about 5 feet. The only novelty in the furnace is found in the layer 



m 



Tferrr 




m 



; mzmE&m&zmm& 



^E2^Z2EEZ22Z^E&m i 



,,,,,,,,,,,,,,,,,, m iiZZZ 



m 



StniONONA-B. 



Fig. 20. — Modified Ekman Furnace — Section. 



of broken fire-brick resting on inclined grate-bars. An inclined 
cast-iron plate extends from the front of the furnace below the 
grate and just above the door, at a distance about two-thirds of 
the length of the furnace. The object of the brick, which are 
loosely arranged in a layer about 9 inches deep, is to cause a more 
perfect mingling of the air and any sulphur vapor present, thus 
insuring more perfect combustion and less subliming. The thin 
iron walls of the furnace radiate heat rapidly, so that it is kept 
quite cool. Ekman claims to reduce the amount of S0 3 formed 
about one-half by the use of the fire-brick ; but where a furnace is 
properly run, there should be no vapor of sulphur passing off, and 



THE SULPHITE PROCESS. 



195 



if an excess of air is admitted, much of the S0 3 is formed beyond 
the furnace in the absorption apparatus. 

Figs. 20 and 21 show an improved style of Ekman furnace built 
of cast-iron in sections which are bolted together. The joints at the 
flanges are made air-tight by some form of asbestos packing. The 
layer of brick rests upon wrought-iron grate-bars, which in this 
furnace are not inclined. The door swings inward, and is so 
balanced that it closes when left open. The amount of air ad- 
mitted is regulated by screwing in the handle which passes through 
the ball counterpoise on the door, so that the end of the handle 




Fig. 21. — Modified Ekman Furnace — Longitudinal Section. 



strikes the furnace and holds the door before the latter has swung 
completely to. Any desired open space may thus be left below 
the door. This furnace has two wrought-iron pans. 

Furnaces of about the dimensions given in Figs. 20 and 21 are 
sometimes built with brick walls lined with fire-brick. The back is 
sometimes in these cases made of an iron plate or casting, and the 
top and front are nearly always so constructed. Some Mitscherlich 
mills use a furnace about 2 feet 6 inches wide, 8 feet long, and 7 
feet high. The furnace is charged through an 8-inch iron pipe, 
passing at an angle through the wall, and which is ordinarily kept 
closed by a flange or cap. 



196 THE CHEMISTRY OF PAPER-MAKING. 

Ill starting up a sulphur furnace of the usual type sufficient sul- 
phur is thrown in to form, when melted, a layer over the bottom 
about one inch in depth. A red-hot bolt thrown into the furnace 
starts the combustion. With retort furnaces, unless working un- 
der pressure, the air supply is regulated by the extent to which the 
door is closed. The open space under the door should never be 
more than one-quarter of an inch high, and with most of these fur- 
naces sufficient air can generally work its way in through the 
cracks around the door. In the Mitscherlich and some other fur- 
naces the doors in front are made air tight and the air supply is 
admitted through a set of air-holes the size of which is regulated 
by a sliding damper. Some such plan as this is to be recommended 
in order to properly control the air supply. 

The most common way of keeping up the supply of sulphur is 
for the workman to raise the furnace door and throw in a few 
shovelfuls as needed. The door is thus opened to its fullest 
extent at frequent intervals, and each time it is raised there is 
a great rush of air into the furnace and through the apparatus. 
In consequence of this the gas is much diluted, even and regular 
absorption is well-nigh impossible, and an excessive and unneces- 
sary amount of S0 3 is formed. It is much better to give the fur- 
nace a considerable supply of sulphur at a time and to make the 
intervals of charging as few as possible. In working the retorts 
under pressure they are charged at intervals of about four hours 
with 200 lbs. of sulphur. Kellner, in order to avoid undue excess 
of air, puts the sulphur in a hopper on top of the furnace, the hop- 
per then being closed at the top and the charge fed in. Mitscher- 
lich feeds through the top or side of the furnace in something the 
same way. Any hoppers or pipes in this position must be so 
arranged as to be kept cool, and must have delivery pipes of good 
diameter, as otherwise there is danger that the sulphur will become 
so heated as to pass into the thick and tenacious condition. Where 
a number of furnaces deliver into one gas main they should be 
charged in regular order, so that the gas may be kept of nearly 
constant composition. 

The whole secret of burning sulphur for the preparation of sul- 
phite liquors lies in the proper regulation of the supply of air. In 
order to convert one pound of sulphur into sulphurous acid there 
is required just one pound of oxygen, or the amount of this gas 
contained in 53.81 cubic feet of air. If much more is admitted, 



THE SULPHITE PROCESS. 197 

and especially if the air is at all moist, there is formed S0 3 and sul- 
phuric acid, which corrodes the pipes and causes a considerable loss 
of both lime and sulphur. The composition of the liquor under 
these circumstances is subject to constant variation. When dolo- 
mite is used as a base the proportion between the lime and mag- 
nesia in the liquor is made to vary as more or less lime is thrown 
down as sulphate, and where magnesia or soda is used the sul- 
phate causes even more trouble by remaining in solution and 
giving to the liquor a fictitious strength. Any considerable excess 
of air is liable also to cause over-heating of the furnace and conse- 
quent sublimation of the sulphur. More sulphur is vaporized than 
can be burned and the unconsumed vapor passes onward with 
the gas until it strikes the colder portions of the pipes or cooler, 
where it condenses, clogging the pipes and causing the formation 
of polythionic acids, as pointed out below. 

Sublimation similarly occurs if for any reason the air supply is 
unduly curtailed after the furnace has become warmed up, since 
under these circumstances there is not enough air to combine with 
all the vapor. 

Colefax and others have shown that sulphurous acid acts on sul- 
phur at the ordinary temperature even in the dark to form thio- 
sulphuric and polythionic acids. This action takes place still more 
rapidly at temperatures as high as 80° or 90° C. These acids are 
very unstable and in most cases decompose on being heated into 
sulphur, S0 2 and S0 3 . The thiosulphates decompose in the pres- 
ence of stronger acids into sulphur and S0 2 . Where these acids 
are formed, as is the case when sublimation and over-heating 
occur, a liquor is produced from which, during the boiling opera- 
tion, sulphur separates out and is precipitated on the pulp. Owing 
to the insolubility of sulphur it is almost impossible to remove it 
in this event, and its presence makes trouble when the pulp is 
used, the sulphur itself rotting the wire cloth and the sulphuric 
acid formed by oxidation rotting the canvas felts. According to 
Mitscherlich and others the presence of these higher acids of sul- 
phur will even completely spoil an entire cook. 

The conditions under which a burner is working may generally 
be inferred with sufficient accuracy from the appearance and char- 
acter of the flame. When the sulphur is burning properly the 
flame is a lazy blue one, sometimes tipped with white. The occur- 
rence of brown fumes, which are the unconsumed sulphur vapor, 



198 



THE CHEMISTRY OF PAPER-MAKING. 



indicates that the furnace is too hot, probably because of too much 
air, and that sublimation is likely to occur. 

The furnace must be cleaned as often as any considerable quan- 
tity of slag and ash accumulates in the pan, and the cleaning must 
be done while the furnace is still hot, since the ash will otherwise 
be so bound together by the sulphur remaining in it that it can 
hardly be removed at all. 

Although sulphur-burning is an apparently simple operation, it 
requires a considerable degree of skill and careful attention on the 
part of the workman. Without these, much more sulphur than is 
needed will be burned, and the excess is more than likely to cause 
not only loss but trouble all through the process. The workman 
should aim to keep the gas as strong as possible and to avoid irreg- 
ularity in its composition. He can only do this by charging the 
furnace in a regular and methodical way and by admitting the 
smallest possible amount of air required to burn the sulphur. 

Copper or iron pyrites are burned in place of sulphur in many 
foreign mills, and they have lately been adopted in one or two 
mills here. Pyrites burners are considerably more difficult to 
handle than sulphur furnaces, and they can only be worked to 
advantage where a number of burners are grouped together so that 
a gas of even composition may be secured. There is considerable 
liability that the burners may become over-heated locally, and 
where such over-heating occurs slags form which are difficult to 
remove and which clog the draft. The most serious objection to 
the use of pyrites is due to the fine dust which is carried along 
by the burner gas, and which, unless entirely removed, causes dirt 
in the liquor and in the pulp. It is usually held back by passing 

the gas in a very slow stream 
through long dust flues of large 
area. 

The ordinary sorts of pyrites 
are, before being burned, broken 
either by hand or some form of 
crusher into pieces of small size, 
the harder sorts being reduced 
to the size of walnuts, while the 
softer kinds may be left in larger lumps. The lumps are burned 
on grate bars in brick kilns or furnaces of the general construction 
shown in Fig. 22, and fitted with doors for charging, regulating 




Fig. 22. — Freiberg Pyrites Burner. 



THE SULPHITE PROCESS. 



199 



the supply of air and removing the cinders. Fig. 22 represents 
two Freiberg burners, one being shown in front elevation and the 
other in sectional elevation. This furnace is especially adapted for 
easily burning ores. The burner is charged through the hole in 
the top and the ore rests upon the triangular grate bars. The round 
bars just above the grate may be worked back and forth from the 
front of the furnace and serve both to break up the ore and to sup- 
port it while drawing cinders. S is the entrance to the gas flue 
built into the brickwork back of the furnace. A small percentage 





Fig. 23. — Section. 



-i/h 



Fig. 24. — Longitudinal 
Section. 



;■ , -..tt^ t. 




w////////////////^^ — ^. 



Fig. 25. — Plan. 
Figs. 23, 24, 25. — The Mitscherlich Pyrites Burner. 



of copper is usually present in the cinder from iron pyrites and its 
extraction partially repays the cost of working the pyrites. 

The Mitscherlich pyrites burners are shown in sections in Figs. 
23 and 24, and in plan in Fig. 25. They are about 1.5 metres 
square in the clear and are lined with Chamotte brick. The top 
is a flat arch with a central opening for the escape of the gas 
into the space between this inner and the upper arch. The upper 
arch has two openings. Two, three, or more burners, according to 
the size of the works, are built side by side, or back to back. Two 
gas flues are built over the burners and the openings through the 
upper arch make into these flues. Any furnace may be cut out by 
closing these openings by means of sand lutes, as shown in the 



200 THE CHEMISTRY OF PAPER-MAKING. 

drawings. The space between the two arches prevents the burn- 
ers from becoming too cool. 

The grate, which is not shown, is about 0.5 metre from the floor, 
and is composed of square bars which may be turned by a key 
from the front in order to shake down cinders. The doors, which 
are in front, are luted with clay or else smeared all over with this 
material. 

For carrying the gas away from the sulphur furnace iron pipes 
may be used as far as the cooler, as the hot, dry gas has little effect 
on this metal. The cooler, and all pipes beyond, should be of 
lead. It is necessary that the pipes should be free from all curves 
in which the sublimed sulphur might lodge beyond easy reach, 
and at all bends or angles crosses should be used to give easy 
access to the interior of the pipes. The flues from pyrites burners, 
for a considerable distance at least, are usually built of bricks which 
have been soaked in coal-tar and which are laid in a mixture of 
tar and sand. As already pointed out, it is absolutely necessary to 
lead the gas from pyrites burners through a dust chamber in order 
to avoid dirt beyond. This chamber, which is usually built high 
enough to admit a man, is divided by numerous partial partitions 
so that it forms a long flue through which the gas slowly passes 
backwards and forwards till it reaches the exit pipe. Similar 
chambers of smaller size and built of unplaned plank may be used 
to advantage where the gas is obtained from sulphur. The rough 
surface of the wood catches the floating sulphur and also removes 
most of the SO s . The chamber should be placed between the fur- 
nace and the cooler. 

The Ritter-Kellner filtering-tower, which is shown in section and 
plan in Figs. 26 and 27, is also well adapted to hold back sulphuric 
acid and sublimed sulphur. The tower is built of brick laid in 
coal tar and sand, and is divided into three compartments, which 
are covered by a slab of slate. The central shaft has a false bottom, 
and is nearly filled with limestone, with which the sulphuric acid 
combines to form sulphate of lime. The tower is washed out from 
time to time by a copious stream of water. 

The means of securing draft through the furnaces and the rest 
of the apparatus varies with the form of absorption apparatus which 
is employed. The method employed by Mitscherlich will be dis- 
cussed when we come to the consideration of the tower. When 
the gas has to be forced through a volume of liquid some form of 



THE SULPHITE PROCESS. 



201 



direct-acting pump is necessary, and the draft is maintained, either 
as in the case of the Partington apparatus, by sucking the waste 
gases from the tanks, or, as in McDougall's system, by forcing air 
into the furnace. Considerably more power is required in the last 
case. In other forms of apparatus, like that of Catlin or the later 




Fig. 26. — The Kellver Filtering-Tower — Section. 



form patented by McDougall, an ordinary fan blower may be used, 
since in these cases the passage of the gas is not impeded. Wher- 
ever their use is thus indicated such blowers are to be preferred, 
as for the same volume of air moved the cost of the blower is 
much less, while it has fewer working parts, and can be run and 



202 



THE CHEMISTRY OF PAPER-MAKING. 



maintained more cheaply. The shell should be lined with 6-lb. 
lead, fastened to the iron by copper rivets, and all rivet heads 
should be carefully burned over with lead. The wheel and all 
other internal parts should be of suitable acid-resisting bronze. 




Fig. 27. — The Kellner Filtering-Tower — Plan. 

The blower is best placed before the coolers, where it takes the hot 
gas coming from the furnaces. 

It has been already pointed out that the rate of absorption and 
the quantity of the gas dissolved by water are mainly dependent 
upon the temperature, the quantity of gas absorbed decreasing 
rapidly as the temperature rises, as shown below : — 



Temp. 


1 vol. of water 
dissolves S0 2 . 


1 vol. of the solution 
contains S0 2 . 


0°C. 


79.789 vols. 


68.861 vols. 


20° " 


39.374 " 


36.206 " 


40° " 


18.766 " 


17.013 « 



It is therefore necessary, in order to obtain the best results in 
liquor-making, that cold water should be used, and that the tem- 
perature of the gas should not be above 10° to 15° C. Where the 
gas is carried in a slow stream through a considerable length of 
cast-iron pipe exposed to the air, it will generally be sufficiently 
cool, except on the warm days of summer. In some foreign mills 
the cooling surface of the pipe is increased very largely by numer- 
ous flanges cast on the pipe. It is desirable in most systems to 
have the liquor plant as compact as possible, and for this reason 
the cooler pipes are often arranged over the furnace, as in Fig. 33, 
pages 211, 212. The pipes are then either cooled by water-jackets 
or by a stream of water trickling over them. 

Fig. 28 shows in section a very efficient and compact form of 
cooler, which is due to Wheelwright. It consists of a tight wooden 



THE SULPHITE PROCESS. 



203 



box about 12 feet long, 3 feet wide, and 3 feet high. Twelve 
4-inch lead pipes are arranged in the box as shown, and pass 
through the ends, where they are flanged over and burned to the 
half-inch lead with which the ends of the box are covered on the 




Fig. 28. — The Wheelwright Cooler. 



outside. A gas chamber, built of half-inch lead and fitted with a 
trap for condensed sulphuric acid and with a pipe for gas, is bolted 
to each end of the cooler. The box is kept filled with cold water, 
which constantly flows in through the supply pipe. This apparatus 
presents a large cooling surface, and the current of gas moving 
through the pipes is very slow. It is easily cleaned, and condenses 
and holds back most of the sulphuric acid. 

Still another cooler is shown on page 211 in connection with the 
Ritter-Kellner liquor apparatus. This is a more expensive form 
than the one just shown, and on account of the cross tubes in the 
cooler pipes the latter cannot be readily cleaned. Difficulty from 
this cause is avoided by the inventors by first passing the gas 
through a filtering-tower, which keeps back the sublimed sulphur. 

Absorption Apparatus. — As already stated in an earlier para- 
graph, the different forms of apparatus in which the bisulphite 
solution is prepared may be conveniently considered with refer- 
ence to two general types, — first, those in which the gas is brought 
in contact with water holding the base in suspension or solution, 
and second, those in which the gas and water react upon the car- 
bonate of the base, which is present in lumps of considerable size. 
To the first class belong the apparatus of Partington, McDougall, 
Catlin, and others, while in the second class are found the towers 
of Mitscherlich, Francke, and Kellner, and the modified towers or 



204 



THE CHEMISTRY OF PAPER-MAKING. 



tank system of the last-named chemist. The later form of Ekman 
tower combines in a measure the features common to both classes. 
The tower, as the oldest and in some respects the simplest form 
of absorption apparatus, will be considered first. It consists essen- 
tially of a high wooden shaft, which may be of various dimensions 
and which is usually of circular section. To prevent leakage the 
joints are often stuffed with oakum and painted with tar. Several 
of these towers are commonly grouped together and surrounded 
and supported by a scaffolding braced by guy ropes. Near the 
bottom of each tower is a heavy grating or false bottom. In the 
high Mitscherlich towers the strain upon the grating is relieved 
by having the main weight of the stone sustained by two heavy 
timbers, which pass through the walls of the tower about two feet 
above the false bottom and which are supported from the outside. 
The towers are nearly filled with lumps of limestone or dolomite. 
In Germany a special form of porous limestone is preferred, but 
most of the similar material found in this country contains rather 
too much iron to be well suited to this purpose, and on that account 
the ordinary dense limestones are commonly made use of here. 
Dolomite is really the best stone for use in the tower, especially if 
a dolomite is selected which pits as it is eaten away by the acid. 

In all forms of towers the gas from the furnaces enters below the 
grating and meets, in its ascent, the descending water, which is 
spread over large surfaces of the stone in a thin film so that the 
gas is rapidly absorbed. The water is delivered at the top through 
a large sprinkler arranged to secure even and regular distribution 
of the water. Many different styles of sprinkler are in use, some 

mills using the crude rose made of 
lead, while others have distributing 
systems of pipe similar to those em- 
ployed on the Glover and Gay-Lussac 
towers in the manufacture of sulphu- 
ric acid. In other cases the water is 
delivered suddenly in some quantity 
at intervals of a minute or two, either 
by a tilting-tank, as in Fig. 29, or 
by apparatus embodying the principle 
of the Tantalus cup, Fig. 30, which 
empties suddenly as soon as the siphon is primed. The sudden 
rush and splashing of the water is thought to secure better results 




Fig. 29. 



THE SULPHITE PROCESS. 



205 




Fig. 30. 



in keeping the tower clear. The simplest arrangement of all con- 
sists merely of a spreading-stone placed under the pipe from which 
water is delivered. 

Fig. 31 shows in a diagrammatic way- 
one form of the Mitscherlich tower and 
accompanying draft tubes. The tower 
is built of wood and varies in height 
from 100 to 135 feet, and in diameter 
from 3 to 5 feet. The dimensions of 
the one from which our figure is taken 
were : Height, 32 metres over all ; height 

of absorption space, 26 metres ; length on each side of tower, 1.2 
metres. Several of such towers are usually built together, the whole 
being surrounded by a scaffolding by which access is gained to the 
top. As most commonly constructed, the towers have only a single 
false bottom. The construction shown in Fig. 31, in which the 
vertical shaft is divided into numerous compartments by a number 
of false bottoms, is on many accounts preferable ; but such towers 
hold less stone and are more difficult to fill and clean. In either 
event the tower is filled with limestone either from the top or 
through the openings marked k. At the top of the tower is a tank 
holding a considerable supply of water and connected with a 
sprinkler just below it. The valve controlling the supply of water 
to the sprinkler is so arranged that it can be worked from the scaf- 
folding around the top of the tower or from the ground. There is 
also a pipe from the bottom of the tank by which, when desired, 
the whole body of water can be quickly discharged, in order that 
the sudden rush of so large a volume of water down through the 
tower may carry along with it the dirt and small stones which 
gradually collect there and at the same time wash out much of the 
sulphate that has accumulated. The leg of the draft pipe nearest 
the tower is often made of glazed earthenware pipe, while the leg 
away from the tower is built up of sections of iron pipe. Contrary 
to the general opinion, these towers do not act like chimneys, for the 
escaping gases are often not only heavier but colder than the out- 
side air. The proper explanation of the means by which the draft 
is maintained is this : the specific gravity of sulphurous acid com- 
pared to air is 2.25, while that of carbonic acid is 1.53. The gases 
coming from the burners consist of sulphurous acid mixed with 
more or less oxygen and sulphuric anhydride and with a large vol- 



206 



THE CHEMISTRY OF PAPER-MAKING. 



ume of nitrogen, and by the time they reach tube B they are all 
well cooled. As result of the reactions which take place within the 
tower, the sulphurous acid and sulphuric anhydride are absorbed, 
the former being replaced by about half its volume of carbonic 



3 m 




Abflus's \ — ' — ~— 



Fig. 31. — Diagram of Divided Mitscherlich Tower. 

Explanation of Terms. — Gasrohr, Gas-pipe ; Stockicerk, Story ; 
Abfluss, Outlet. Dimensions are in metres. 

acid, and the latter by its equivalent of that gas. In spite there- 
fore of the greater height of the tower, the column of gas within 
it weighs less than the shorter column of gas in tube B, so that 
there is a constant upward flow and escape of gas from the top of 



THE SULPHITE PROCESS. 207 

the tower. That the gases in the tower are under this slight press- 
ure may be shown by boring into the tower at any point when the 
draft, instead of being inward, as is the case with the chimney, is 
from within outward. It is necessary, however, in order to secure 
this draft, that the tube B should have a length of at least 153 
inches for every 225 inches in the height of the tower, and by 
increasing the length of B over that called for by this proportion 
the force of the draft may be augmented to any necessary extent. 
The fall of the heavy column of comparatively cold gas in B draws 
over continually a fresh supply of hot, and therefore lighter, gas 
from the burners. 

A number of difficulties is likely to arise in working towers. 
It is hard to secure always an even distribution of the water as it 
falls through the tower, and similarly to properly spread the gas as 
it passes upward. Gutters are very likely to form through cutting 
away of the stone at one point more than another, and any such 
tendency increases rapidly after the first appearance of the hole. 
The stone is usually thrown into the tower from the top, but in the 
process of working the lower lumps of stone are continually eaten 
away, and being pressed upon by the stone above may pack together 
and clog the tower as the upper stone falls down. If the stone 
becomes wedged at any point in the tower, arches are. likely to 
form, and, as the stone below is eaten away, an open space of con- 
siderable size may result. Finally the arch breaks, and the stone 
above, settling suddenly, may so pack together as to impede the 
draft. Such arches may usually be broken before they cause 
serious trouble by blows from a heavy mallet against the outside of 
the tower. Their existence is made evident by the hollow sound 
given out when suspected portions of the tower are similarly 
struck, but this involves so much labor as to be hardly practicable. 
The last traces of gas are almost never absorbed in the tower, and 
the unabsorbed portion is frequently so considerable as to cause a 
high percentage of loss. Crusts of monosulphite and sulphate of 
lime not unfrequently become so extensive as to impede or almost 
stop entirely the flow of gas. Crusts of monosulphite are espe- 
cially likely to form if the gas is weak or if the supply of water is 
curtailed. For these reasons it is necessary to inspect the condi- 
tion of the stone at frequent intervals, and to either loosen it up by 
a crowbar, or to remove it altogether and refill the tower with fresh 
stone. The old stone is piled up in the air and allowed to weather, 



208 



THE CHEMISTRY OF PAPER-MAKING. 



in order to cause the incrustation to loosen and flake off. These 
difficulties may be avoided in large part by making the tower 
somewhat conical in shape, so that the stone in working down 
comes into a wider and wider space. 

The strength and quality of the liquor made in towers depend 
upon the amount and strength of the gas passing into the tower, 
the quantity and temperature of water with which the tower is 
supplied, and the amount and condition of the limestone. The 
composition of the gas and liquor at different heights in the tower 
has been studied by Harpf, to whom we are indebted for the fol- 
lowing table. The tower from which the samples were taken was 
divided, as shown in Fig. 31, into twelve sections by false bottoms, 
ten of the sections containing limestone. The percentage by 
volume of sulphurous acid in the gas at the different stories on two 
different days is shown below : — 



Percentage of S0 2 by volume. 



On Oct. 17, On Oct. 19, 



Draft tube at I 
First story . 
Second story 
Third story 
Fourth story 
Fifth story . 
Sixth story 
Seventh story 
Eighth story 
Ninth story 
Tenth story 
Eleventh story 
Twelfth story . 



about 5.54 

4.62 
3.42 
2.77 
2.31 
1.95 
1.57 
0.92 



8.92 

7.52 
7.42 
6.25 
6.96 
5.83 
5.13 
3.78 
2.29 
1.29 
1.16 



(?) 



Beginning of the absorption space. 



Exit for gases. 
Water reservoir. 



It will be noticed that there is a continual and quite regular 
decrease in the percentage of sulphurous acid toward the top of 
the tower. No tests were made at the first story, as the liquor 
fell through this to the outlet. The tests of the 17th were made 
from below upwards, and had to be discontinued at the ninth story, 
as it had become dark. The tests of the 19th were made in the 
forenoon in the reverse order, or by starting at the top and work- 
ing down. The figure obtained at the fifth story is probably 
erroneous. At the eleventh story the gas escaped into the air, and 



THE SULPHITE PROCESS. 



209 



it will be seen that there was then present 1.16 per cent, of S0 2 , or 
about 13 per cent, of the amount originally present. This of course 
was lost. The gas is cooled in its ascent, so that the absolute 
volumes change, but each volume of S0 2 absorbed sets free an 
equal volume of C0 2 , so that the proportions of S0 2 in the total 
volume at the different points are directly comparable. 

The composition of the gas and liquor at the different stories on 
another day is given in the results of the 

Experiments of October 23, 1888. 



Percentage 

S0 2 in 
gases (by 
volume). 



Percentage of S0 2 in liquor 
(by weight). 



Total. 



Free. 1 Combined. 1 



Remarks. 



Draft tube . 
First story . 
Second sto'ry 
Third story 
Fourth story 
Fifth story . 
Sixth story . 
Seventh story 
Eighth story 
Ninth story . 
Tenth story 
Eleventh story 
Twelfth story 



7.70 

7.28 

8.19 (?) 

7.90 (?) 

6.32 

7.18 (?) 

5.59 

4.36 

2.58 

1.90 

1.27 



3.056 
2.662 
2.848 
3.968 
1.344 
1.488 
0.672 
0.304 
0.082 
0.520 



2.608 
2.208 
1.984 
2.688 
0.832 
0.784 
0.426 
0.192 
0.049 
0.520 



0.448 
0.454 
0.864 
1.280 
0.512 
0.704 
0.246 
0.112 
0.033 



(?) 



(?) 

Gas exit. 
Water reservoir. 



It should be noted in connection with these tables that in Ger- 
many the sulphurous acid, present as sulphite of lime, CaS0 3 is 
called " combined acid," while the entire excess over that amount 
is spoken of as "free acid." This nomenclature has been followed in 
these tables, although in this country all the acid present as bisul- 
phite of lime is called "combined acid," while the term "free acid" 
is limited to the amount present in excess of that needed to form 
bisulphite. The German "free acid" might, perhaps, better be 
called "available acid," since it is the only portion which is effec- 
tive in the process. 

An examination of the table brings out the fact that the liquor 
in the eleventh story consisted merely of a solution of the gas in 
water which forms the true sulphurous acid, H 2 S0 3 . In the gas 
1 See remarks in text immediately following table. 



210 THE CHEMISTRY OF PAPER-MAKING. 

analyses the figures at the third, fourth, and sixth stories do not 
show the expected decrease in the percentage of S0 2 by volume. 
This may have been due to inequalities in the gas caused by irreg- 
ular work at the burners. It will also be noted that the liquor 
from the fifth story is stronger than any taken lower down. Harpf 
considers that the difference here found is a real one, due to the fact 
that the lower stories contained comparatively little limestone, and 
that there was sufficient oxidation to reduce the strength of the 
liquor. We have frequently observed a similar loss of strength in 
case of finished liquors which were exposed for a time to the fur- 
ther action of the gas. In the present case, however, as Harpf sug- 
gests, the discrepancy may have been due simply to guttering. 

The tower upon which these experiments were made was supplied 
with gas from pyrites burners, and in other tables given by Harpf 
the proportion of S0 2 present in the burner gas by volume ranges 
from 2.30 to 13.30 per cent. The average figure is about 7.5 per 
cent. 

Before taking these samples the liquor flowing from the tower 
stood 6° Be. and contained — 

Per cent. 

Free sulphurous acid 3.232 

Combined sulphurous acid 0.768 

Total 4.000 

while at the conclusion of the tests it stood 5|° Be. and con- 
tained — 

Per cent. 

Free sulphurous acid 2.944 

Combined sulphurous acid 0.896 

Total 3.840 

Ekman, as already stated, at first prepared the solution of bi- 
sulphite of magnesia used in his process in small towers about 
5 feet in diameter and 14 feet high. These were filled with cal- 
cined magnesia, but as this material even in large lumps rap- 
idly softens up and becomes pasty under the action of the water, 
while, moreover, it is impossible to calcine the magnesite without 
producing a large proportion of material too fine to be used in a 
tower, he was compelled to abandon them and adopt a modified 
tower working upon quite a different principle. This tower is 
built of heavy sheet lead, supported by a stout framework of tim- 



THE SULPHITE PROCESS. 



211 



ber, and is about 20 feet square by 60 feet in height. It is filled 
above the false bottom with flints, and milk of magnesia instead of 



ffopper 






Wustc G<ls 




Fig. 32. — Eitter-Kellner Tank Apparatus. 

water is delivered at the top in an intermittent stream. This is 
spread in thin films over the surface of the flints and rapidly absorbs 



212 



THE CHEMISTRY OF PAPER- MAKING. 



the gas, with the formation first of monosulphite and then of bisul- 
phate of magnesia. The chemical reactions in a tower of this form 
are essentially the same as those occurring in the common form of 
tank apparatus. As with other forms of towers, there is a consider- 
able escape of sulphurous acid from the top. 

Fig. 32 shows a form of liquor apparatus which has been patented 
and worked by Bitter and Kellner, and which combines in consid- 
erable measure the features of both towers and tanks. The por- 
tion of the apparatus in which the liquor is made consists of a set 
of four closed tanks, (7, D, E, jF, each provided with a perforated 




\\\\\\^\\\\N\\\\\\^ 

Pig. 33. — McDougall Liquor Apparatus. 

false bottom upon which rests the limestone with which the tank 
is about three-quarters filled. The tanks are filled with water to a 
point just above the limestone. The gas from the burners after 
passing through the purifier A and cooler is drawn by the gas 
pump G- up through the tanks and D in succession, being first 
delivered through the perforated pipe coiled beneath the false bot- 
tom of tank C, and bubbling up through the water on its way to 
tank D, up through which it similarly passes. As the gas is being 
continually sucked away from D by the pump, both and D are 
working under a partial vacuum. The gas which has been drawn 
from D is then forced by the pump into tank E below the false 



THE SULPHITE PROCESS. 



213 



bottom, and as it passes upward into pipe 5 it is similarly forced 
along through F. By this time all the sulphurous acid has been 
absorbed and the waste gases escape from F through the pipe G-. 
As the liquor-making progresses fresh water is from time to time 
run in through a pipe in the top of F, from which tank it can be 
transferred into E as needed, through the pipe h. On account of 
the pressure in tank E the liquor in E can be transferred to D 
whenever the valve in the pipe i is open, and from D may be run 
into (7, which like D is under a partial vacuum. 




-777- 



Fig. 33. — McDougall Liquor Apparatus. 



The chemical reactions taking place in the tanks are similar to 
those which take place at what may be called the corresponding 
stories in the tower. The gas is first absorbed by the water, to form 
a solution of sulphurous acid, which reacts upon the limestone, set- 
ting free carbonic acid and forming in the first case sulphite of lime. 
The gas passing along through the tanks in series gradually loses 
all, or nearly all, its sulphurous acid and becomes more and more 
highly charged with the carbonic acid which passes away with the 
waste nitrogen. After a time, as the water takes up sufficient gas, 
the sulphite is dissolved with the formation of bisulphite, and when 



214 THE CHEMISTRY OF PAPER-MAKING. 

the liquor in tank C has reached the desired strength it is drawn off 
and replaced by weak liquor from the tank next in series, the others 
being similarly emptied and filled, until the last tank is charged 
again with fresh water. 

This apparatus has not, so far as we know, come into use in this 
country. The novel form of cooler to which reference was made on 
page 203 should be noticed. Its construction is clearly shown in 
plan arid section in Fig. 2. The cooling surface is greatly increased 
by numerous cross tubes in the cooling-pipes, as shown at b 2 in Fig. 
3. These cross tubes are open at the ends so that the water passes 
through them. Figs. 2 and 3 are sub-figures in Fig. 32. 

The apparatus patented by McDougall and used with some mod- 
ification by Partington is shown in Fig. 33, and either in this or 
its modified arrangement is the type which has been most generally 
introduced in this country. As used by McDougall it consists of 
three tight tanks fitted with agitators and with pipes by which the 
gas coming from the furnace is discharged near the bottom of the 
first tank and is carried onward through the series, as indicated by 
the arrows. The tanks are nearly filled with milk of lime, which 
may be transferred from one tank to the other through the pipes S. 
Gf Gr on each tank are gauges with glass tubes, in which the level 
of the liquid in the tanks may be seen. The sulphur is burned in 
the retort under a pressure of 3 to 5 lbs., which is maintained by 
an air compressor, and the gas passes through a series of water- 
jacketed cooling-pipes before passing into the first tank. All the 
tanks are first charged with milk of lime, and as soon as the liquor 
in vat No. 1 comes to test it is drawn off into settling-tanks ; the 
valves between the absorbing-tanks are then opened, and fresh milk 
of lime is run into the last tank until the level of liquor in all 
three is again brought to the proper point. 

Although a somewhat better absorption of gas is secured, several 
disadvantages present themselves when sulphur is thus burned 
under pressure. A great amount of steam is required for the air 
compressor, and there is difficulty in keeping the tanks tight. 
Rather more sulphur is burned, and the danger of sublimation and 
formation of polythionic acids from overheating is considerably 
increased. The proportion of S0 3 formed is also greater than 
where the combustion proceeds slowly under the normal or slightly 
diminished pressure. In a retort working under pressure about 
3 lbs. of sulphur are burned per hour per square foot of pan 
surface. 



THE SULPHITE PROCESS. 



215 



In the Partington apparatus, Fig. 34, similar tanks are used, but 
they are placed one above the other and the gas is drawn through 
them by a pump connected to the pipe by which the waste gases 
leave the highest tank. As used by Partington, there is a con- 
tinuous flow of liquor through the apparatus, fresh milk of lime 
running constantly in a carefully regulated stream into the upper 




LIQ UQH OUTLET 




Sasi.-uet 



Plan 

Fig. 34. — Partington Liquor Apparatus. 



tank, while a corresponding amount of finished liquor overflows 
from the lowest tank nearest the furnaces. In the United States 
the discharge of liquor from this apparatus has generally been 
intermittent, the charge in the bottom tank being brought to test 
and drawn off before the charges in the other tanks are transferred, 
and fresh milk of lime run into the upper tank. 

The liquor apparatus employed by Wheelwright overcomes the 



216 



THE CHEMISTRY OF PAPER-MAKING. 



difficulties encountered when the gas is forced through a consider- 
able column of liquid, and is so constructed that the gas has a free 
passage over the surface of the liquor, which is exposed to its 
action in thin films. It permits the use of an ordinary fan blower 
in place of the much more expensive gas pump, and there is con- 
sequently a considerable saving of power. The apparatus consists 
of three horizontal cylinders built of 3-inch Southern pine staves, 




Fig. 35. — McDougall's Later Apparatus. 



and placed one above the other. The cylinders are usually about 
20 feet in length, and either 5 or 6 feet in diameter. Short and 
heavy bronze shafts ending inside the tanks in a head, to which 
the heavy wooden shaft is secured, pass through stuffing-boxes 
secured to each head of the tank. To the wooden shaft is attached 
a system of paddles, arranged like those on a stern-wheel steamer. 
The tanks are filled with milk of lime or magnesia up to the level 
of the shaft. The gas enters the bottom tank above the surface of 
the liquor, and passes along over it through the three tanks in 
succession. The shaft revolves about eighteen times a minute, 
and as each paddle comes out of the liquor the latter is exposed to 
the gas, partly as spray and partly as the thin film adhering to the 
paddle. The conditions for absorption are so favorable that the 



THE SULPHITE PROCESS. 



217 



capacity of this apparatus is practically limited only by the amount 
of sulphurous acid gas passed through it. With the proper num- 
ber of . sulphur furnaces, 2500 gallons or more of liquor, standing 
6° Be., may be obtained per hour. The only difficulty which is 
likely to be experienced is due to the tendency of the monosulphite 
of lime to crystallize upon the paddles in the second cylinder. As 
patented by Catlin the apparatus is discharged intermittently. 

The second and later form of liquor plant employed by Mc- 
Dougall is shown in plan in Fig. 35, and is in principle essentially 
the same as the apparatus just described. The cylinders marked A 
are arranged so that they may be rotated by worm and gear ; A 2 is 
a stationary tank of the ordinary form, with an air-tight cover and 
agitator. Attached to the interior of the vessel A are projections, 
a, intercepted by transverse partitions, a 2 , with central apertures, a 3 , 
to allow of the passage of the gas and liquid through the vessel. 
These projections as they move carry with them a portion of the 
liquid and shower it upon the gas, whilst the transverse partitions 
prevent an immediate flow of the liquid from one end to the other. 
The level of the liquid is such as to leave a passage for the gas 
over its surface. D are connecting pipes for the passage of the 
gas and liquid from vessel to vessel. The milk of lime is stored in 
the tank D 2 , and its flow is regu- 
lated by a tap. A continuous cur- 
rent of sulphurous acid gas enters 
the apparatus at E, and meets 
successively a shower of liquid in 
the rotating vessels, while much 
of the liquid is also exposed to 
its action as a film upon the par- 
titions. The gas and liquid move 
in opposite directions, the course 
of the gas being shown by the 
dotted arrows and that of the 
liquid by the full arrows. This 
apparatus is evidently well 
adapted to secure a rapid and 
complete absorption of gas. We 

have not seen it in operation, but it must be difficult to clean, and, 
except in the tank next to the furnace, troublesome crusts of mono- 
sulphite must be likely to form upon the partitions and projections. 




218 



THE CHEMISTRY OF PAPER-MAKING. 




Fig. 



Ritter-Kellner Towers. 



The apparatus shown in Fig. 36 is described in the French 
patent No. 157,754, quoted by Hoyer and Schubert. A is a water 
tank, D a tank partly filled with limestone, and is another reser- 
voir for water. The fur- 
nace gases are drawn along 
the pipe, B, by the action 
of the injector, B, which 
works by water from the 
tank, A. The descending 
water carries the gas down 
to D, where it passes up 
through the liquor in which 
the limestone is submerged, 
and escapes through R' and 
R" into C, where it bubbles 
through the water therein 
contained before making its 
final exit. A portion of the waste gases is, however, drawn back 
by B and sent around again. The pump, P, keeps the liquor in 
circulation by drawing from D and discharging into A. The con- 
tents of are, when 
necessary, trans- 
ferred to A, after 
which is again 
filled with fresh 
water. 

Frank has em- 
ployed a tower 
which is, in its gen- 
eral principles, sim- 
ilar to that of 
Mitscherlich. The 
apparatus at first 
brought out by 
Ritter and Kellner 
consists of five tow- 
ers of moderate 
height, shown in sectional elevation in Figs. 37, 38, and in plan in 
Fig. 39. In connection with the towers there is sometimes worked 
a set of tight boxes filled with lumps of limestone, and shown at 




Fig. 38. — Ritter-Kellner Towers. 



THE SULPHITE PROCESS. 



219 



Q in Fig. 40. A second set of boxes is shown at R, and these may 
be filled with the carbonate of another base, as magnesite. The 
gas enters under the false bottom of tower B, and, after passing up 
through the limestone 
in the tower, is carried 
along by a pipe to the 
bottom of the next tower, 
and so on through the 
series. The tower, F, is 
supplied with fresh wa- 
ter, and the weak liquor 
flowing from this tower ?t 
is pumped up and sent 
through E, D, and C in 
succession. It is at this 
stage charged with con- 
siderable free acid, and 
is sent through the boxes 
Q, where it takes up an 
additional quantity of 
lime. From Q it is sent 
through B, where it 
meets the strong gas, 
and after leaving this tower it is sent through the second set of 
boxes, B, to take up the desired quantity of the second base. 
When it is desired to obtain a liquor carrying a greater proportion 
of gas to base than is secured when limestone is used in the towers, 
certain or all of them may be filled with coke or some substance 
which is not acted upon by the solution. 

The Ritter-Kellner towers are in this country built of wood, and 
are commonly 5 feet in diameter and about 25 feet high. The use 

of the boxes, Q, and of coke in 
any of the towers has, we believe, 
been generally discontinued as in- 
troducing unnecessary complica- 
tion. As at present worked, the 
group of five towers may be re- 
garded as a single Mitscherlich tower, built in sections which are 
placed, for convenience, on the same level. The difficulties in 
working them are similar in kind though rather less in degree to 
those encountered with the Mitscherlich tower. 




Fig. 39. — Ritter-Kellner Towers. — Plan. 




Fig. 40. 



220 



THE CHEMISTRY OF PAPER-MAKING. 



The Nemethy liquor apparatus, which is shown in plan and in 
sectional elevation in Fig. 41, is similar in principle to the Kell- 
ner apparatus just described, but is rather simpler in detail. The 
four towers, B, are packed with limestone, as are also the two 




Fig. 41. — The Nemethy Liquor Apparatus. 

tanks, C. The gas enters the system at o M and passes, as will be 
noticed, down the first tower. It then enters the bottom of the 
second tower, through which it passes upward. From there it 
passes down the third tower, and up the fourth, which it leaves at 



THE SULPHITE PROCESS. 



221 



o 2 . Water enters through the branched pipe, H 2 , and is delivered 
at the top of the towers through the sprinklers, b. The liquor 
flowing from the towers enters the bottom of the limestone tanks 
through the pipe r x . Here any excess of S0 2 reacts upon the lime- 
stone, while the sulphate of lime settles out as the liquor slowly 
rises. The clear liquor 



runs off through r 2 into 
the storage tank, A. 
By means of the pump, 
P, the liquor, if below 
test, may be again 
drawn from A and 
sent through the sys- 
tem. 

The Wendler-Spiro 
liquor apparatus is 
shown in Fig. 42, in 
which are the sub-fig- 
ures 1 and 2. Only 
the absorption appara- 
tus is here shown. The 
complete plant com- 
prises also a very large 
cast-iron retort, which 
is kept submerged in 
water, and in which 
the sulphur is burned 
under pressure ; an air- 
pump ; a subliming 
box or chamber for 
holding back sulphuric 
acid and sublimed sul- 
phur ; and a cooler of 
efficient form. 




Fig. 42. — The Wendler-Spiro Liquor Apparatus. 



Fig. 1 is a sectional view of the apparatus. Fig. 2 is a top view 
of the lower part of the same, partly in section, the letters A, B, C, 
and D indicating the vats. 

K is the absorption chamber, provided with drip shelves a a, 
the vats and the chamber being connected by a system of pipes. 
The lime-water necessary for the liquor enters the vat D by the 



222 THE CHEMISTRY OF PAPER-MAKING. 

pipe 11. The sulphurous acid enters the vats A, B under pressure 
by the pipe 1, and passes either through A, K, and D, or B, K, 
and D, the lime-water passing either through D, K, and A, or i>, 
K, and B. The gas cannot be completely absorbed by the liquid 
in the vats A, B, on account of the rapidity with which it passes 
through it, and therefore the absorption chamber K, provided with 
drip shelves a a, is put in, which affords the gas the largest possi- 
ble plane of attack. It is the object to let the weak liquor, which 
is still able to absorb a large quantity of sulphurous acid, run as 
often as possible over the shelves in the saturating chamber K, 
whereas the strongest liquor, which is unable to absorb much more 
sulphurous acid, is finally charged with gas in the lower vats. 
The incomplete liquor passes from A or B through the pipe 2 to 
C, and from C through K back to A or B. The liquor is com- 
pleted in either A or B, and then passes through the pipe 2, 2' to 
the place of consumption. The vat D is used for the reception 
of lime-water, and the vat for the reception of the weaker 
liquor. 

The system of piping by which the vats A, B, (7, Z>, and the 
chamber K are connected is as follows : The gas is conducted to 
the vats A, B by the pipe 1, and from A, B to the saturating cham- 
ber K by pipes 5 and 6, from K to the vats C, D by the pipes 9 and 
10 — the partial object of 10 being to allow the free flow of the 
liquid from the vat C when the valve 8 is opened. The liquids are 
conducted through the pipes 7 and 8 into K, from there by the 
pipes 3 and 4 to A B, and from these vats they may be carried 
to the outlet 2' or to the vat C by the pipe 2. 

Suppose the vats A and B are already filled with weak liquor. 
C is empty, and D contains lime-water. The gas enters through 
the pipe 1 into the vats A and B, and up through the saturating 
chamber K to D. The valves in the pipes 7, 8, and 9 are then 
closed, and the valve B 2 in the pipe 2 is opened. Pressure will 
then increase in A, B, and K until it is sufficient to force the 
weak liquor from B to C. As soon as this is accomplished, the 
valve 8 is opened, and the weak liquor is allowed to pass from O 
over the shelves in the saturating chamber K, and then through 
the pipe 4 to the vat B. On this passage it will absorb the gas 
which is in K. The outflow of C is regulated in such a. manner 
that as soon as B is nearly filled the liquor in A will also nearly 
have absorbed the desired amount of sulphurous acid. 



THE SULPHITE PROCESS. 223 

As soon as this is accomplished, the gas is switched over to B, 
and the outlet valves from iTare again closed, and the completed 
liquor is forced over from B to the pipe 2 2' to the place of con- 
sumption. As, meanwhile, chamber K is under pressure of sul- 
phurous acid, the lime which has settled in chamber K will be 
dissolved, and thus it is possible to obtain a liquor containing an 
equal percentage of lime; and also in this manner the drip shelves 
of the chamber iT will be kept clean, thus excluding the possibility 
of an obstruction in the chamber K. When all of the completed 
liquor has been forced out of the vat A or B, fresh lime-water will 
be conducted into such empty vat by opening the valve in the 
pipe 7 and allowing the lime-water to run over the shelves a of the 
chamber K to the vat A or B. By closing the gas outlet valves 
of K the weak liquor is forced from A to C. Then by opening 
the valve 8 the weak liquor is allowed to pass from Q over the 
saturating shelves a a of the chamber K to A. After the same 
liquid from one of the lower vats — say A — has passed over the 
saturating shelves in K twice, the liquor in the other lower vat — 
say B — is nearly completed. The gas is then switched over and 
conducted through the vat A, the outlet valves from K are closed, 
and the completed liquor is forced from B through the pipe 2 2' 
to the place of consumption. 

In this case the apparatus is worked under gas pressure; out 
the same effect would be obtained by suction. The circulation of 
the liquids could likewise be obtained by pumping. 

The Behrend liquor apparatus which is commonly used in mills 
working the Salomon-Brungger process is very similar to the 
apparatus of Wendler and Spiro, but lacks the absorption box 
which adds greatly to the efficiency of the latter plant. The 
Behrend apparatus is in fact practically a Partington plant with- 
out agitators, agitation being secured by the upward passage of 
the gas. 

The liquor apparatus of Dr. Frank is shown in plan and 
elevation in Fig. 43, for which we are indebted to Schubert's 
" Cellulosefabrikation." Although this apparatus has been in use 
in many continental mills, it has not, so far as we know, yet 
found a place in this country. It is, however, to our minds, one 
of the best which has thus far been devised, and we take pleasure 
in introducing it to the favorable consideration of American paper- 
makers. 



224 



THE CHEMISTRY OF PAPER-MAKING. 



Iii the figures, A represents a closed sulphur oven in which 
combustion is maintained by the air-pump B, which is provided 
with the air-chamber (7, to equalize and regulate the pressure. 
The gas from the furnace passes first into the sublimator D, in 
which most of the sulphur which may have been carried over is 




r. 1 



7 v ?;:,;;>;>, . ■; ,:■;' — y/yyy..-.. , . \.yyy yy : :::>:■/.::.;,,; ,y.:y:y; "".■;,"<: i":": — ": • y.\yy>/>r-: A - i •';■.■•,;;';////„ 



■■wyy,. 




Fig. 43. — Dr. Frank's Liquor Apparatus. 



condensed, the remainder being caught in the dust-chamber E. 
After passing through the cooler, the gas is sent through the 
small washing tank 1, which is partially filled with water, to hold 
back any sulphuric acid which may be present in the gas, and 
from this washer there may be drawn from time to time a weak 
sulphuric acid for use about the mill. 2, 3, and 4 are absorption 
vessels fitted with vertical agitators, and the gas passes through 



THE SULPHITE PROCESS. 225 

them in the order of their numbers. Tanks 2 and 3 are closed, 
and work under pressure, but No. 4 is generally open, and is the 
one into which the fresh milk of lime is charged. The milk of 
lime is made up very strong, and absorption goes on in the last 
two tanks until the liquor in them is beyond the monosulphide 
stage and well along toward bisulphite. The charge in 3 is then 
transferred to 2, being at the same time diluted with sufficient 
cold water to bring the finished liquor to the proper boiling 
strength. It will be noticed that, for this reason, tank 2 is made 
considerably larger than the others. There is, of course, always 
some heating up of the liquor in the two smaller tanks ; but the 
evil effects of this are corrected by the admission of so large a 
volume of cold water, which is in the best condition for the rapid 
absorption of gas. It ordinarily requires only about 3 minutes 
to bring the monosulphite in solution in tank 2, and finish off the 
liquor. The air-pump is then stopped, and the combustion of 
sulphur ceases for the time. The finished liquor is then drawn 
off, and a fresh charge from 3 transferred to 2, while the tanks 3 
and 4 are being refilled with fresh milk of lime. The charging and 
emptying take about 30 minutes, and the whole operation about 7 
hours. The capacity of the apparatus is from 30 to 35 cubic metres 
for the small size, or from 54 to 60 cubic metres for the large size, 
for 24 hours. It can be arranged to run continuously, but Dr. 
Frank prefers the intermittent method, as results may thus be 
better controlled. 

In this apparatus, Dr. Frank has used lime, magnesia, and soda, 
and, where desirable, can bring the test of the liquor up to 10° B. 
The guarantee given with the apparatus is that 95 per cent, of the 
sulphur burned shall be brought into the liquor in a form avail- 
able for use ; or, in other words, for every 100 kilogrammes of 
sulphur burned, there shall be obtained in the liquor, 190 kilo- 
grammes of sulphurous acid. In practice, 193.6-194 have been 
obtained. 

Dr. Frank, acting upon the theory that the work of the liquor 
is effected by the free sulphurous acid, advises the preparation and 
use of liquor with as small a content of lime as possible. This is 
entirely in accord with our own views, and the point is one which 
deserves much more careful attention from pulp-makers than it 
has yet received. It should be borne in mind that by " free acid " 
Dr. Frank has reference to all the gas present in the liquor in 



226 THE CHEMISTRY OF PAPER-MAKING. 

excess of that required to form monosulphite with the base 
present. 

In discussing the working of his apparatus, Dr. Frank offers the 
following as an example of an , ordinary factory liquor of 7° Be, 
and made in an apparatus other than his own : — 

Sample A. 

Per cent. 

Free sulphurous acid 2.35 

Combined sulphurous acid 2.00 

Total 4.35 

Lime 1.75 

For comparison with this, he submits a liquor of barely 5° Be, 
made in his apparatus, and which pulped the wood in the same 
length of time as above, without any separation of sulphite. The 
composition of the liquor was as follows : — 

Samjyle B. 

Per cent. 

Free sulphurous acid 2.382 

Combined sulphurous acid 0.874 

Total 3.256 

Lime 0.764 

It will be noticed that this liquor, although of less specific 
gravity, and containing a smaller total of sulphurous acid, is 
nevertheless richer in available acid than A. Sample A required 
23 kilogrammes of sulphur per cubic metre, while B required only 
17 kilogrammes. The ash of the pulp cooked with A was 1.85 
per cent., while that from the pulp cooked with B was only 
0.36 per cent. 

A liquor used at the Krumauer Fabrik, working under the 
Mitscherlich system, had the composition shown below : — 

Per cent. 

Free sulphurous acid ........ 2.023 

Combined sulphurous acid 1.012 

Total 3.035 

Lime 0.827 

and required only 16 kilogrammes of sulphur for a cubic metre. 
In spite of the fact that less sulphur was used to make this liquor, 



THE SULPHITE PROCESS. 



227 



it is a more expensive liquor than B, which took 17 kilogrammes, 
because the proportion of free acid in B is so much greater that 
B is the more efficient liquor, and can therefore be used in less 
amount. 

In these different forms of apparatus in which milk of lime is 
used, it is perhaps somewhat less trouble to work them in the 
continuous way, but the quality of the liquor is more easily con- 
trolled when the liquor is carried through in separate charges. 
Each charge can then be tested for strength, and dumped as soon 
as it comes to test. It is important that the finished liquor should 
be removed from the absorption tank as soon as possible, as other- 
wise it is liable to be weakened through the formation of sulphuric 
acid. It is easier to settle out the last portions of monosulphite 
than to try to bring them into solution, and considerable time 
may thus be saved. Besides, the greater portion of the iron which 
was present in the lime does not go into solution until nearly all 
the sulphite is dissolved, and there is less danger from contamina- 
tion from this source when the liquor is drawn off before it is 
entirely clear. 

The quality of the lime used in the preparation of these liquors 
is of the first importance, and its value for this purpose increases 
with the amount of magnesia it contains. 

The dolomites found at Bowling Green, Ohio, and at several 
points in the State of New York, are especially good, and carry, 
in some cases, after burning, over 40 per cent, of magnesia. The 
lime should, of course, be well burned, should slake easily, and be 
as free as possible from lime and silica. The following analyses 
will indicate the general composition of lime well suited for use 
in this connection : — 



Silica, etc 

Iron and alumina sesquioxides . . . 

Lime 

Magnesia 

Carbonic acid, water, etc., by difference 



0.05 


0.30 


0.65 


1.54 


57.09 


55.99 


40.88 


40.32 


1.33 


1.85 



trace 

0.18 

57.79 

40.24 

1.79 



If lime which has been improperly burned, or which has become 
air-slaked, is used, the proportion of base is likely to vary to such 
an extent as to cause trouble, and such limes are not so readily 
acted upon by the gas. The usual proportion for making up the 



228 THE CHEMISTRY OF PAPER-MAKING. 

milk of lime is 200 lbs. of lime per thousand gallons, and this 
should give a liquor of 9° or 10° T., carrying about 3.50 per 
cent, of sulphurous acid. The liquor made in towers runs from 
7° to 10° T., and usually contains a slightly greater proportion 
of free sulphurous acid, or acid above that needed to form bisul- 
phite, than the liquor which is made from milk of lime. It is 
difficult to make a lime liquor in practice of a greater density than 
10° T., but where magnesia or soda is used without lime the 
magnesia liquor can be made in an apparatus like Catlin's to stand 
25° T., while the soda liquor can be brought up to 60° T. 

The following analysis may be taken as representative of a well- 
made liquor prepared from dolomite : — 

Bisulphite Liquor. 
Specific gravity at 15° C. = 1.0582. 

Per cent. 

Sulphurous acid (S0 2 ) 4.41 

Sulphuric acid (S0 3 ) 0.13 

Lime (CaO) 0.95 

Magnesia (MgO) 0.72 

Silica (Si0 2 ) 0.04 

Combined as : — 

Sulphate of lime (CaS0 4 ) 0.22 

Bisulphite of lime (CaS.>0 5 ) 2.84 

Bisulphite of magnesia (MgS 2 5 ) . . . 3.04 

Free sulphurous acid (S0 2 ) 0.11 

The lime and magnesia in a finished liquor never bear quite the 
same relation to each other as in the dolomite from which the 
liquor was prepared. The magnesia is always somewhat in excess, 
as a portion of the lime is unavoidably thrown out as sulphate and 
monosulphite. In case any great discrepancy appears, it is evidence 
that too much air has been admitted to the sulphur furnace, or 
else that a large proportion of lime is being lost as monosulphite 
in the sediment. An analysis of the sediment will point to the 
proper explanation. 

Although the loss of both lime and sulphur may easily be con- 
siderable, it is so insidious that it will probably be underestimated 
unless careful daily records are kept of the amounts of lime and 
sulphur used, the volume of liquor made, and the quantity of each 



THE SULPHITE PROCESS. 229 

chemical which analysis shows to be present in the liquor. Good 
liquor may be made even where large losses occur, since the loss 
comes wholly upon the lime and the sulphur combined with it, 
so that as more lime is lost the proportion of the more desirable 
bisulphite of magnesia in the liquor is increased. 

The loss of sulphur is due to dirt and ash, to subliming, escape 
of gas through imperfect absorption, and, especially, to the forma- 
tion of sulphuric acid on account of a successive supply of air. 
The loss from dirt should not amount to more than 2 per cent., 
and 5 per cent, should cover all loss from moisture, ash, and sub- 
limed sulphur. Unless great care is exercised the loss through 
formation of sulphuric acid may easily amount to 20 or 30 per 
cent. There should be no excuse for any loss of sulphur through 
imperfect absorption of gas. If the lime used has not been freshly 
slaked, or if it has become air-slaked in storage, a considerable loss 
will always be found between the lime in the liquor and that 
weighed off, on account of the absorption of water and carbonic 
acid from the air. If an inferior grade of lime is used, it is likely 
to contain considerable silica, which will be left in the sediment. 
Improperly burned lime carries more or less carbonic acid, and 
consequently more of such, lime must be used to obtain the same 
strength of liquor. The greater part of the loss of lime is due to 
failure to bring all the monosulphite into solution, and to the 
formation of sulphate. The sediment in the storage tanks should 
be tested before it is thrown away, as it may 
pay to work it over if the proportion of 
monosulphite is very large. 

It sometimes happens that the sulphite of 
lime formed in the middle or upper tanks 
crystallizes upon the paddles of the appara- 
tus instead of going into solution. This 
crystallization usually takes a peculiar form, 
which gives the paddles the appearance of 
having kernels of popped corn stuck over 

them. The thickness of the deposit may Fig. 44. -Incrustation 
i i t -i -i OF CaSO,. 

become so great, unless promptly attended 

to, as to cause the breaking down of the paddles, and, in any 

case, the power required to drive the apparatus thus incrusted 

becomes much greater than usual. 

Fig. 44, which is taken from a photograph of a piece of paddle 




230 THE CHEMISTRY OF PAPER-MAKING. 

from one of these machines, will serve to give an idea of the thick- 
ness sometimes reached by this incrustation. Perhaps the easiest 
way to remove the deposit is to let down one or two charges of 
water instead of milk lime. As the gas is dissolved by the water, 
the sulphite gradually goes into solution. 

It is claimed on good authority that the addition of a small 
amount of Solvay ash to the milk of lime causes much better 
absorption of the gas, and more rapid settling of the liquor ; while 
it is also said to prevent the precipitation of sulphite of lime in the 
digester. The ash is added in proportion of 2 to 5 per cent, on 
the weight of the lime, and with it is used about the same weight 
of common salt. If the desired result is not obtained, the amounts 
of each are increased in successive charges of liquor, about one- 
half per cent, of salt being added for each additional per cent, of 
ash. Soda crystals without the salt are sometimes used in the 
proportion of 40 lbs. to 1000 gallons of milk of lime. This is 
equal to about 20 lbs. of anhydrous carbonate of soda. 

In the Crocker process, which makes use of a solution of bisul- 
phite of soda, prepared by agitating monosulphite of lime in a 
solution of neutral sulphate of sodium and then charging the mix- 
ture with sulphurous acid, crude acid sulphate of soda is roasted 
to obtain the neutral sulphate, and the sulphite of lime may be 
made by adding lime to the waste boiling liquor. This last method 
is claimed by the patentee as the preferable one; but when the 
waste liquors are so treated, a large quantity of organic matter 
comes down with the sulphite and makes the separation difficult. 

Pumping. — Rotary pumps, so placed that the liquor flows into 
them under a slight head, are best used in all cases for pumping 
sulphite liquors. The pump should never be placed where it is 
necessary to prime it, or use a foot- valve on the suction-pipe. It 
is impossible to keep such a foot-valve tight, owing to the crys- 
tallization of monosulphite in the working parts. The pump should 
be built of phosphor-bronze, or other bronze of good acid-resisting 
quality. In some foreign mills an acid egg similar to those used 
for vitriol is employed for pumping liquor. The egg is a lead-lined 
vessel, provided at the top with a pipe through which air may be 
forced under pressure. The liquor is run into the egg through 
one pipe until it is nearly full ; the valve on this pipe is then 
closed, and air forced in on top of the liquor, by which means the 
liquor is driven out through the delivery pipe leading from the 



THE SULPHITE PROCESS. 231 

bottom of the egg. Steam injectors have been used in some mills 
in this country for transferring liquor. There is no objection to 
their use, if the liquor is discharged directly into a closed digester, 
otherwise considerable sulphurous acid is lost through the heating 
of the liquor. Where nothing is to be gained by such heating, 
the use of the injector is too expensive. 

Storage Tanks. — The tanks used for storing liquor may be 
lined with 6-lb. sheet lead for the sides, and 8-lb. for the bottom. 
No lining whatever is necessary when the tanks are of the ordinary 
circular form. In such cases, however, the tanks should always 
be first made tight, with water or steam, before any liquor is 
admitted. If this is not done, it is impossible afterward to make 
them tight, on account of the crystallization of monosulphite be- 
tween the staves. The storage tanks should be covered so as to 
prevent escape of gas, and access of air, though it is not necessary 
that the cover should be perfectly air-tight. The tanks should be 
so placed that the sediment may be easily washed out from time 
to time. When the liquor is stored in quantity, there is little 
loss of strength, either through escape of gas or oxidation to 
sulphate. 

In order to obtain clear liquor with as little loss of time as 
possible, the delivery pipe from the tank should be attached to 
some form of float, so that, in pumping, liquor would always be 
drawn from the top. A sufficient length of stout rubber hose may 
be used inside the tank, and should be attached to the bottom with 
a lead pipe leading to the pump. The other end of the hose is 
attached to the float, which may be a box of sufficient size, made 
of copper, and hermetically sealed. Wood soon becomes so satu- 
rated with the liquor as to be useless for the float. The best 
form of gauge showing the height of liquor in the tank is a glass 
tube, of a diameter of not less than ^-inch. The fitting which 
secures the tube to the tank at the bottom should be a cross with 
a cock on both the horizontal and vertical arms, for convenience 
in keeping the tube from clogging with the sediment. 

The best results in cooking are only obtained where the whole 
liquor apparatus is so run as to secure liquor of a quality as nearly 
uniform as possible. This necessitates close attention to the sul- 
phur-burning, air-supply and the strength and quality of the milk 
of lime. No lime from a new quarry should ever be used until its 
composition has been ascertained by analysis, and the weight to 



232 



THE CHEMISTRY OF PAPER-MAKING. 



be used corrected by proper allowance for any impurity it may 
contain. 

Digesters and Digester Linings. — The extremely corrosive 
action of sulphurous acid and bisulphites upon iron renders some 
form of lining necessary for protecting the digester shell. All 
forms of iron are rapidly attacked by the acid, especially at the 
high temperatures and pressures employed in this process ; wrought 
iron suffers most severely. Corrosion does not proceed regularly 
over the surface, but instead the iron is deeply pitted. Steel 
resists somewhat better than wrought iron, and cast iron suffers 
least of all. 

Fig. 45 is from a photograph of a piece of half-inch wrought- 
iron boiler plate cut from one of the digesters at the mill of the 
Richmond Paper Company, and shows very 
well the extent to which the corrosion may 
proceed. The digester from which the sample 
was cut had been in use two and a half years, 
under conditions which it is only fair to say 
were much harder than any likely to be 
tolerated now. 

The curious irregularity with which the 
metal was corroded is especially noticeable. 
The iron was eaten away to a depth of 
3^-inch for some distance along a line just 
above the bottom row of rivets on several 
of the plates. In other places, from -| to -^- 
inch of the metal was gone. The average 
depth to which the shell was corroded was 




Eig. 45. — Corroded 
Digester Shell. 



at least -^-inch. 



Lead is the only common metal which 
resists perfectly the action of the liquor, and its immunity from 
corrosion is largely due to the almost complete insolubility of 
its sulphate, which, as soon as formed, makes a protective coat- 
ing for the metal underneath. The use of lead in this connec- 
tion is greatly complicated by the peculiar behavior of the metal 
when subjected to frequent variations of temperature over con- 
siderable range. The coefficient of expansion of lead is 0.0000297, 
while that of iron is only 0.0000123 ; so that wherever the two 
metals are held together and subjected to any rise of temperature, 
there is a constant tendency for the lead to pull away from the 



THE SULPHITE PROCESS. 233 

iron; or, in the ease of a lead lining contained within an iron 
shell, the tendency is for the lining to grow too large for the 
shell. This tendency is exaggerated still more by the peculiar 
fact that when lead has been expanded by heat, it does not, like 
most metals, resume its original dimensions upon cooling, but, 
apparently owing to the sluggish movement of its molecules, it 
covers somewhat more surface than before, being made at the 
same time correspondingly thinner. This causes the phenomenon 
known as " crawling," the lead showing a tendency to pull away 
in one direction from any point at which it is held. If held by 
bolts, the bolt-hole is gradually changed in form from a circle to an 
ellipse, while if the lead is secured through the flanges of the 
digester sections, it gradually crowds out through them. 

Owing to this continual movement, cracks are likely to appear 
wherever the lead makes a turn which is at all short. The crack 
usually does not come at just the point of turning, but parallel 
with it, and a little to one side. 

Contrary to the usual fact in regard to metals, the acid-resisting 
qualities of lead are considerably enhanced by the presence in the 
lead of certain impurities in small amount. 

Calvert and Johnson, upon whose researches the following table 
is based, took lead plates, each 1 metre square, and covered them 
with 16 litres of sulphuric acid each. After ten days the quantity 
of lead sulphate formed was determined. 



I. 
II. 


Specific gravity of 
acid used. 

1.842 
1.705 


Ordinary lead, 
grms. PbS0 4 . 

67.70 
8.35 


Virgin lead, 
grras. PbS0 4 . 

134.20 
16.50 


Pure lead, 
grms. PbSO. 

201.70 
19.70 


III. 


1.600 


5.55 


10.34 


16.20 


IV. 


1.526 


2.17 


4.34 


6.84 


V. 


1.746 


49.67 


50.84 


55.00 


VI. 


1.746 


51.91 


54.75 


57.41 



The ordinary lead contained : lead, 98.82 ; tin, 0.40 ; iron, 0.36 ; 
copper, 0.40. The virgin lead : lead, 99.21 ; tin, 0.01 ; iron, 0.32 ; 
copper, 0.44. In the first four experiments pure acid was used, and 
at the ordinary temperature ; in the last two, commercial acid at a 
temperature of about 50° C. 

Other experiments indicate that small quantities of antimony 
and copper make lead more resisting ; while, when bismuth is 
present, the lead is more readily attacked. 



234 THE CHEMISTRY OF PAPER-MAKING. 

The whole object of the many ingenious mechanical devices 
which have been embodied in the lead linings of sulphite digesters 
is to hold the lead in place, while at the same time localizing and 
diminishing the tendency to crawl. The thickness and weight of 
the lead employed varies within wide limits from the 6-lb. lead 
used in the Mitscherlich process to -|-inch lead, weighing 48 lbs. to 
the square foot, as at one time used in several mills in this country. 
Generally speaking, the thickness of the lead is ^-inch, correspond- 
ing to a weight of 32 lbs. per square foot. 

The present rapid introduction of cement linings has so changed 
the conditions of the sulphite process that lead-lined digesters now 
have hardly more than a historical interest. They have played 
so important a part in the development of the process, however, 
and so much skill in chemical engineering has been expended upon 
their construction, that we shall consider briefly the more important 
of the different types. 

One of the earliest devices for holding the lead in place is found 
in the rings employed by Frank. These were at first merely 
formed of lead and antimony cast in half-circles, and burned 
together inside the digester. In a later form, advantage was taken 
of the greater expansion shown by brass, and the rings were made 
of brass covered with lead ; the ring thus held more tightly as the 
temperature in the digester rose. Still later the ring, instead of 
being continuous, was formed in three segments, held in place by 
wedges, which could be tightened up as the lead underneath the 
ring grew thinner. The great objection to all forms of ring is 
found in this tendency to cut and squeeze the lead beneath so 
rapidly that frequent repairs are necessary. In a modified form, 
however, rings have been used in several of the most satisfactory 
lead-lined digesters with which we are acquainted. In these cases 
the rings were made of wrought-iron strips 2 inches wide, cut in 
half-circles, and sprung in place inside the digester. They were 
then covered with f-inch lead, which was burned to the lining on 
either side. The rings were placed 18 inches apart through the 
whole length of the digester. 

Partington has employed several different methods for holding 
the lining in place in his globe-shaped rotaries, and they are all of 
interest in connection with the study of the development of digester 
linings. The lead itself is cut in sections, having the form of a 
spherical triangle or lune, each piece being of sufficient size to 



THE SULPHITE PROCESS. 



235 




Fig. 46. — Clamp. 



cover y 1 ^ of the interior. In the earlier linings the joints at 
the junction of the various pieces were burned, so that the lining 
formed one continuous piece. It was held in place by bolts with 
large washer-shaped heads, the washer being on the interior and 
the nut on the outside. These heads were 
covered with lead of the same thickness as 
that used for the linings, and the covering 
was burned around the edge to the lining. 
Rows of clamps of the form shown in Fig. 
46 extended from what may be called the 
poles of the digester, in lines similar to those 
marking parallels of longitude on the globe, and a similar row of 
clamps passed round the digester ecpuatorially. The heads of the 
clamps were formed of iron surrounded by cast lead. They were 
held in place by bolts passing through the digester wall, and 
secured with a nut on the outside. Makin introduced an improve- 
ment (Fig. 47) in these linings 
by the use of a compound lead 
and iron plate, formed of a sheet 
of thin boiler iron perforated with 
numerous half-inch holes, and 
covered with lead, which was cast upon it and secured by the 
metal which flowed through the holes. An objection was made to 
this cast lead on account of the numerous pin-holes, which were 
difficult to avoid in casting the metal, and Makin's lining was next 
prepared by taking a sheet of lead of the usual thickness used in 
lining, laying the iron plate upon it, which in this case was per- 
forated in such a way that the holes were considerably smaller at 
the end next the lead than upon the upper side, and pouring melted 



c?9 




Fig. 47. — Makin Lining. 




lead or solder into these holes. Rolled sheet lead could then be 
used, and as only one side of 
the iron was covered, there 
was considerable saving in the 
former metal. A somewhat 
similar lining was adopted by 
McDougall, who used, in place 

of the iron plate, stout iron-wire gauze to which the lead was 
burned. G. W. Russell patented in this country a compound 
lining, formed by casting lead upon a heavy wire gauze or net- 
ting, as shown in Fig. 48. 



Fig. 48. — G. W. Russell's Lining. 



236 



THE CHEMISTRY OF PAPER-MAKING. 



Fig. 49 represents a digester of the type known as a globe 
rotary, lined up with the Makin compound plates. As this lining 
was at first applied, the joints between the sections b were covered 




Fig. 49. — Partington Eotary Digester. 

by strips of sheet lead, shown as a heavy black band at e. These 
strips were soldered or burned to the adjacent edges of the lining. 
A later form of the Partington lining made use of the modifica- 
tion introduced by Springer. In this method, which is shown in 

Fig. 50, the sections of the 
lining are so placed as to 
leave a small space between 
adjacent edges. In the figure, 
A represents the boiler shell, 
and a the compound lead and 
iron plate, invented by Makin. 
is an acid-resisting packing 
of asbestos, or asbestos and rubber, between the edges of the 
plates. Over the joint is laid a strip of sheet packing, t. The 
sections of the lining are held in place by means of stay strips i?, 




Fig. 



50. — The Springer Lining. 



THE SULPHITE PBOCESS. 



237 



composed of a perforated metal band, e, around which lead has 
been cast after the method followed in making the lining itself. 
The stay strips are secured by bolts, which occur at frequent inter- 
vals, and whose heads are covered with lead as shown. 




Fig. 51. — The Ritter-Kellner Lining. 

The Ritter-Kellner digesters are of upright form, and for holding 
the lead in position the main reliance is placed in two devices; 
the first of these consists of a lead, or lead and 
antimony ring sunk in the digester wall, as 
shown at E in Fig. 51, and to which the lead is 
burned. The digester wall between these rings 
is perforated at various points, and rivets, 6r, of 
hard lead are driven in the holes, the lining 
being burned to them on the inner side. The 
iron shell presents a perfectly smooth interior, 
all joints being butt joints, and all rivets 
counter-sunk. 

The earliest form of the Ekman digester 
which was introduced into this country was of 
small size, having a capacity of only about 500 lbs. of pulp, and 
was lined with. 16 lbs. lead. At the upper portion of the digester 




Fig. 52. — Early 
Ekman Lining. 



238 



THE CHEMISTRY OF PAPER-MAKING. 



wall a recess of the form shown in Fig. 52 extended around the 
digester, and the lead lining was forced into this recess for support. 
A better method for causing the lining to crack could hardly 
have been devised, and so far as we know none of these digesters 
are now in use. The sectional digesters of Wheelwright which 
succeeded them also gave much trouble in their early form, 
owing to the cracking of the lead below the flanges, and the 
difficulty of making joints between the sections. An attempt was 
made to overcome this by making the lining continuous, and burn- 
ing it to lead rings which passed between the flanges. We are 
of the opinion that this is a fairly good form of lining, but at the 
time of its adoption there was much trouble from collapsing, caused 
by liquor which had worked its way between the lining and the 
shell, only to be again converted into steam when the digester 
was blown off. 

The principle of the Wheelwright cast-iron digester, which was 
designed to overcome the difficulties arising from the expansion 
and crawling of the lead lining, is illustrated in Fig. 53, which 
shows a section through one ring. The rings were 6 1 - or 7 feet in 




Fig. 53. — Wheelwright Cast-Ikon Digester (Section through One Eing). 

diameter and 2 feet high. The digester was built up of ten of 
these rings, with top and bottom cone pieces. It will be noted on 
inspection of the figure that the inner wall of each ring curves out- 
ward toward the flanges, so that the lining always lay upon convex 
curves, while any expansion was at once taken up through the 
flanges. The joints at the flanges were made tight either by a 
packing like that of Jenkins or by lead rings placed just inside the 
bolt holes, at which point a slight depression will be noticed. 

The Graham boiler is built up of compound lead and iron plates, 
and has the lead lining secured to the iron at every point of con- 
tact. The compound plates are prepared before the sheets are bent 
or assembled. The iron plate is cleaned and smoothed very care- 



THE SULPHITE PROCESS. 239 

fully by an emery wheel. It is then placed over gas jets, and upon 
it is put a rectangular frame or ledge, the joint between the frame 
and ledge being made tight by a fireproof packing. The upper sur- 
face of the plate which is to receive the lead is moistened by zinc 
chloride solution, and when the temperature of the plate has been 
raised by the gas jets to about the melting point of lead, the molten 
lead is poured on. In this way a very good joint between the two 
metals is secured, and it is claimed that it is impossible to cut 
away the lead with a cold chisel without leaving a thin coating of 
this metal upon the iron plate. An uncoated margin for the joints 
and rivets is left on each plate, and after the plates are assembled, 
the unprotected lines along the joints are similarly coated by heat- 
ing locally with a blow-pipe and running in melted lead. 

The difficulties inseparably connected with the use of the best 
lead linings led to the introduction of digesters built of bronze, 
capable of resisting more or less perfectly the action of the sul- 
phite solution. The general formula for these bronzes is 9 parts 
of copper to 1 part of tin ; but each manufacturer has his own 
method of working the alloy, and thus claims to secure special 
properties. 

Martin L. Griffin gives the composition of the Schenck digester 
metal as below : — 

Per cent. 

Tin 7.68 

Copper 91.28 

Zinc . 0.89 

These digesters are usually built of the cast metal in 3-foot 
sections, having in some cases a diameter as great as 9 feet ; the 
joints between sections are easily made tight with lead rings, as 
there is here no lining to be cut. It is undeniably true that all 
such digesters are acted upon to a considerable extent by the hot 
liquor, as may be readily proved by taking some of the unwashed 
pulp, drying and burning it, dissolving the ash in weak acid, and 
then placing for a moment a polished knife-blade in the solution, 
when the copper will be deposited upon the iron. 

Besides the corrosion which, in spite of chemical testimony, was 
for a long time denied by the builders of these digesters, they are 
subject to other and perhaps more serious elements of weakness. 
Recent tests show that the strength of the metal is, in some cases, 
reduced fully 40 per cent, by heating to the temperatures reached 



240 



THE CHEMISTRY OF PAPER-MAKING. 



in practice in these digesters, while the frequent changes of tem- 
perature to which they are subjected cause in time a crystallization 
of the metal, which greatly impairs its power to resist strain. 
The significance of these facts has been emphasized by several 
disastrous explosions. 

There is some difference of opinion as to the relative merit of 
the upright and rotary form of digester. Somewhat less liquor 
can be used in the rotary, and there is no danger of making black 
chips, as none of the chips remain uncovered for more than a 
minute or two at a time. The upright digesters are somewhat 
cheaper to build and keep in operation, and although we have no 
satisfactory explanation to offer for the fact, we have found it to 
be generally true, that pulp made in an upright is of somewhat 
stronger and better quality than that produced in the rotary. 

Many forms of blow-off valves are in use on sulphite boilers, 
and a poor valve causes endless trouble. It may be said, in 
general, that gate valves are not well suited for use in this posi- 
tion, on account of their great liability to become clogged from 




Fig. 54. — Clapp Valve. 



pulp which has got into the bonnet of the valve or on the seat. 



Plug cocks are better. 



The Clapp valve (Fig. 54) has been used with great success in 
the soda process, and possesses many points of merit which should 
make it readily adaptable to sulphite digesters. Its construction 



THE SULPHITE PROCESS. 



241 




Fig. 55. — Burning- Iron. 



and the readiness with which it may be cleaned are apparent from 

the figure. 

The steam-pipes on rotary digesters necessarily pass through the 

trunnions, and usually follow the curve of the digester for a short 

distance on the inside. 

In the upright digesters, 

steam is always admitted 

at the bottom, and best 

through a 3-inch pipe. 

Various devices have 

been used for spreading 

the steam as it issues from the pipe ; but they are objectionable, 

since the force of the steam is thereby much diminished, and there 

is considerably more likelihood of clogging the pipe by pulp or 

incrustation. With the steam-pipe placed at the apex of a properly 

shaped cone bottom, the chips themselves spread the steam suffi- 
ciently, and there is no danger that any of the 
chips will pack to one side, where the steam 
will not reach them. 

All lead-burning inside the digester is done 
with a blow-pipe, but joints can be more 
quickly made with heavy lead by the use of 
the burning-iron, whenever the seam is hori- 
zontal. 

Fig. 55 shows the shape commonly adopted 
for such irons, which usually weigh about 16 
lbs. Where much lead-burning of this sort 
has to be done, it is advisable to employ one 
of the recently invented irons, which are kept 
hot by an electric current, since by their use 
much time is saved, and the plumber's helper 
can usually be dispensed with. 

A good form of plumber's gas-machine for 
use in lead-burning is shown in Fig. 56. It 
consists of two cylinders made of heavy sheet 
lead, or two oil barrels may be taken, and 
lined up with thin sheet lead. The vessels 
are connected by a rubber tube at the bottom, 

as shown. The lower cylinder has a false bottom, and the space 

above this is filled with granulated zinc, made by melting the 




Fig. 56. — Gas 
Machine. 



242 THE CHEMISTRY OF PAPER-MAKING. 

metal and pouring it in water from the height of a few feet. 
The upper cylinder is filled with dilute sulphuric acid, which, 
upon opening the cock, flows down into the lower cylinder, 
and by its action upon the zinc causes the rapid evolution 
of hydrogen. The gas is led away to the blow-pipe through 
a rubber tube which is attached to the small pipe leading from 
the top of the bottom tank. The pressure of the gas may be 
regulated roughly by the height at which the upper cylinder is 
placed. The apparatus is self-regulating, because, as soon as the 
cock in the gas-pipe is closed, the pressure of the gas soon forces 
the acid up into the higher cylinder, and away from the zinc. 
The evolution of gas then stops until a new supply is required. 

The Mitsclierlicli Digester is noticeable from its large size, 
and the fact that it was the first type in which bricks were used 
as a portion of the lining. These boilers are commonly from 
12-14 feet in diameter, and from 36-40 feet long. Those of 
the smaller size hold about 100 cubic metres of wood and 60 cubic 
metres of liquor. They have two manholes at the top, and two or 
three at the bottom, and are mounted on foundation walls at least 
as high as a man. There is so much expansion in these boilers 
that they are not fastened directly to the walls, but instead are 
supported by cast-iron shoes riveted to the shell, and resting upon 
iron beams. Sometimes rollers are placed between the shoes and 
the beam, while often the adjacent surfaces are merely planed to 
give a well-faced bearing. 

The Mitscherlich lining consists, first, of a coat of tar and pitch, 
which offers some protection to the shell, and also acts as a cement 
to hold the lining of thin sheet lead, which is next applied. Upon 
the lead are laid two courses of special acid-resisting bricks, formed 
with tongue and groove, by which they interlock. Portland 
cement is sometimes used with the bricks, which in any case are 
laid flat in the first course, and edgewise in the second. In some 
foreign mills, a second layer of lead is placed between the bricks. 

The boilers are heated by a series of hard lead pipes, which 
cover the lower third of the inside. The pipes are arranged in 
four sections of coils, each of which is independent of the others. 
The steam ends of alternate coils are at the same end of the boiler, 
so that the steam in the adjacent coils is passing in opposite 
directions. The total length of pipe in a single digester is from 
1200-2600 feet. The digesters are fitted with safety-valve, ther- 



THE SULPHITE PB0CES8. 243 

mometer-tubes, and gauge-cocks to which a tube is temporarily 
attached to indicate the level of the liquor while charging the 
digester. There are also cocks by which samples of liquor may be 
drawn for test during the cook. 

Smaller upright digesters in two sizes are offered by the owners 
of the Mitscherlich patents, the sizes being 16 x 10 and 24 x 14. 

The expense and difficulty which attend the operation of even 
the best types of lead-lined boilers have caused the chemists and 
others engaged in the development of the process to look long 
and carefully for some other means of protection which should 
prove more manageable and less costly. One of the earliest at- 
tempts in this direction is described in United States patent 
351,330, granted to one of the authors. In this case, the interior 
of a cast-iron digester 6 inches in diameter by 20 inches high was 
coated with an enamel composed of one part of borate of lead to 
ten parts of litharge. This enamel has a low fusing-point, is very 
tenacious, and resists the action of the liquor at least as well as 
lead. The difficulty of perfectly coating so large a casting proved 
so great, however, that only one digester thus protected was 
put in operation, and this developed numerous spots where scale 
beneath the enamel prevented its adhering to the metal. At 
about the same time, a white enamel was brought forward by 
Frambach. 

The present greatly improved methods of lining up digesters 
are the result, in the main, of the work of Pierredon, Brungger, 
Mitscherlich, Wenzel, and Kellner, in Europe, and of G. F. Russell 
and Curtis and Jones, in this country. 

The Salomoii-Brimg-ger Boiler. — About 1883 Brungger, who 
was chemist in Salomon's mill at Cunnersdorf, was led in the 
course of some temporary repairs to substitute within a digester 
a short length of iron pipe for the bronze one by which steam was 
ordinarily supplied. Upon examining this pipe at the end of the 
cook, he found it firmly coated with a thin but dense scale of 
sulphite of lime, which had apparently protected the metal from 
corrosion . Acting upon this hint, he soon had a digester in opera- 
tion, in which, by appropriate means, this scale was formed over 
the entire interior as a substitute for the lead lining previously in 
use. It is necessary, in order to secure the coating, that the heat 
be transmitted through the metal to the liquor within ; and for 
this reason digesters of this type are heated by a steam jacket. 



244 THE CHEMISTRY OF PAPER-MAKING. 

In its present form the Salomon-Briingger boiler consists of two 
distinct parts ; an inner shell of welded steel which is from 6 feet 
6 inches to 7 feet in diameter, and an outer shell, also of steel, but 
riveted. The cone and throat of the inner shell are of cast bronze, 
and to this cone is riveted the outer shell or jacket. In order to 
allow for differences in expansion, the joint between the two shells 
at the bottom is made by a stuffing-box. The total length over all 
is about 30 feet. In all its mechanical features this digester merits 
the highest praise. 

In order to secure the protective coating, the pressure in the 
jacket is brought to about 40 lbs. before the liquor is admitted. 
The latter upon coming in contact with the hot metal is decom- 
posed in part, and there is deposited over the metal a thin but 
excessively hard and impervious crust of sulphite of lime, with 
perhaps some sulphate. It is claimed, and, as we believe, properly, 
that a crust Jg-inch thick (2-3 mm. Reuleaux) affords complete 
protection. There is at most "a merely superficial blackening of the 
shell. No especial reliance is placed upon the acid-resisting quality 
of the bronze cone, but this, like the steel shell, is protected by the 
lining. In order to secure protection at this point, the digester 
is complete^ filled with liquor up to within a few inches of the 
manhole cover. With the expansion of the liquor it becomes nec- 
essary to blow off a little from time to time, when, in case the 
liquor falls below the level indicated, sufficient water is pumped 
in to supply the deficiency. The liquor itself is used clear, and 
is the ordinary bisulphite solution. 

With each successive cook the scale increases somewhat in 
thickness, while any places which have been laid bare where the 
lining has flaked off are freshly coated. Too thick a lining is 
undesirable, not only because the tendency to flake off is much 
increased with any irregularit}^ in thickness, but also because the 
thicker scale unnecessarily retards the transmission of heat into 
the boiler. For this reason it is customary about once a month, 
or when the scale has reached a thickness of about ^-inch, to 
remove the scale by hammering. The same result may be attained 
by the use of a more acid solution, but this necessitates the prep- 
aration of a special liquor, and is otherwise objectionable, as there 
is some danger that the metal may be corroded. 

The records of the mill at Cunnersdorf show that whereas in 
a certain digester 210 boilings were made in a given length of 



THE SULPHITE PROCESS. 245 

time when working with a lead lining, 300 boilings were made 
in this digester in the same length of time after adoption, of the 
protective crust. 

The Jung- and Ldndig method of lining depends upon the forma- 
tion, upon the digester wall, of a coating of the double silicate of 
iron and lime, protected further by one of silicate of lime. Before 
applying the lining the inner surface of the digester is first thor- 
oughly cleaned with wire brushes and a strong alkaline solution. 
This is followed by a wash of dilute sulphuric or hydrochloric acid 
to remove the alkali, and the excess of acid is rubbed off with 
waste. 

The clean surface of the metal is then painted with ordinary 
sulphite liquor made from lime, with the result that a thin coat 
of the double sulphite of lime and iron is formed. After this is 
dry it is brushed over with a solution of water glass, in order to 
obtain the double silicate of calcium and iron ; and this coat is also 
allowed to dry, and then repeated. The coating of double silicate 
so obtained is finally covered with a pasty mass from 1 to 5 centi- 
metres thick, of a mixture of dry calcium monosulphite and water 
glass. The proportions used are 5 to 30 parts by weight of the 
monosulphite and 50 parts by weight of water glass. If desired, 
100 parts of ground Chamotte, quartz sand, powdered glass, or 
asbestos powder may be added, according to circumstances. The 
proportions of the various ingredients may be changed as desired 
to produce the object in view, which is a solid, adhering, earthen- 
ware-like coating, which should become quite hard. 

The digester is now ready for the first boiling with sulphite 
solution, causing the formation of soluble sodium sulphite which 
goes into solution, and of silicate of lime in the hardened mass. 
The latter compound is very acid-resisting, and is capable of pro- 
tecting any metallic surface from the erosive action of sulphurous 
acid. It is advisable to repeat the coating of monosulphite and 
water glass, with or without the addition of such bodies as quartz 
sand, etc., after a few boilings, so as to obtain several layers of 
silicate. Valves and tubing after being cleaned, as above described, 
are filled with a solution of bisulphite of lime and well warmed ; 
then emptied, filled up with water-glass solution, emptied, and 
dried. They are then boiled in a solution of bisulphite of lime, 
and treated again with water glass, repeating this process until 
a sufficiently thick coating of silicate is obtained. 



246 THE CHEMISTRY OF PAPER-MAKING. 

The mixture of water glass and monosulphite of lime soon grows 
hard, and constantly becomes denser and harder, in contact with 
sulphite solution; further, the coating sticks very closely to the 
iron or steel, owing to the presence of what corresponds to a rust 
cement ; and finally, the difference between the coefficient of 
expansion affects only the fifth decimal place, and hence can be 
assumed to be identical with that of iron. 

Cement Linings. — Various linings composed of so-called acid- 
proof cements are at the present writing being rapidly introduced 
in this country and abroad. One of the earliest as well as one of 
the most successful of these cement linings is that of Wenzel. 
By his method cement blocks are formed in wooden molds made 
to conform to the curvature of the different portions of the 
digester, and are then assembled and cemented in place within 
the boiler. The special cement used is for the most part a mix- 
ture of Portland cement and silicate of soda. The thickness of 
the blocks varies with the size of the boiler and the position for 
which the block is intended ; those for the bottom of the digester 
being made thicker, to withstand the greater wear. The usual 
limits of thickness are from 60-200 mm. Rotaries having a diam- 
eter of 2.5-3 metres require a lining 80-100 mm. thick, while 
70-80 mm. is sufficient for those of 2-2.5 metres diameter. The 
blocks for a 4-metre Mitscherlich boiler are made 125 mm. in 
thickness. 

After lining by this system, the boiler is heated by steam for 
several hours, to a temperature of 140°-160° C. By this treat- 
ment, cracks are opened in thin or weak places, and are cut out 
and refilled. The heating is then repeated until no more cracks 
appear. The lining is finally completed by covering the blocks 
with a coating of the very fine cement, which is put on to a depth 
of 4-5 mm. This wears away in two to three months, but may be 
replaced in a few hours. 

Wenzel, in some cases, first lines the digester with iron wire 
lath, upon which the cement lining is then formed. 

Kellner has several recent patents for cement linings, among 
them being the British patents numbered 6951, 15,930, 15,931, all 
issued in 1890. Kellner's cements are made of ground slate and 
silicate of soda, or of powdered slate and glass and Portland 
cement, and they are either put on in the plastic condition, or in 
the form of blocks or slabs. In one case the digester is first lined 



THE SULPHITE PROCESS. 247 

with the mixture of ground slate and silicate of soda, and after 
this has set, a second layer, composed of one part ground slate, two 
parts ground glass, and one part Portland cement, is applied. 
Kellner has also patented in this connection the use of a lining 
composed of slabs of tempered glass laid upon such a cement 
backing. 

G. F. Russell, at Lawrence, began experiments with cement lin- 
ings, applied directly to the shell in the plastic state, about 1888. 
In the earlier linings, a mixture of Portland cement and sand was 
used, but the sand was found to detract, if anything, from the 
durability of the lining, and his present excellent results are 
obtained by the use of Portland cement alone. This is in most 
cases reinforced by a facing of special brick or tile, as shown in 
Fig. 57. The usual thickness of the cement lining is about four 




Fig. 57. — Russell Lining. 

inches. Where an old digester is relined by this method, this, of 
course, involves a serious curtailment of production ; but since the 
introduction of these linings the general tendency has been to 
build the new digesters of very much larger size. The shape of 
the upright digesters has also been materially changed to good 
advantage. In place of the well-known cone at top and bottom, 
the top is now formed by gradually drawing in the shell in a gentle 
curve, starting nearly from the centre, as shown in Fig. 58, which 
is taken from one of the digesters recently built for. the Waldhof 
Zellstoff-Fabrik. The dimensions given are in millimetres. Some 



248 



THE CHEMISTRY OF PAPER-MAKING. 



digesters of this type building in this country have the bottom 
formed after the same manner as the top here shown. These 




Fkj. 58. — Cement-lined Upright Digester. 

forms of construction possess the advantage of much diminishing 
the tendency which the older forms had to spring slightly under 
pressure, and so open cracks in the cement where the cones joined 



THE SULPHITE PROCESS. 249 

the body of the boiler. The throat at either end may be protected 
by a bronze or lead sleeve passing down flush with the lining. 
Either metal beneath the lining or bronze or lead and antimony 
pipes passing through it is likely to cause cracks, due to the 
greater expansion of the metal. 

All cement linings are more or less porous when first applied, 
but in use soon fill up with sulphate and sulphite of lime. They 
then become practically impervious to the liquor, and afford com- 
plete protection to the shell beneath. Such liquor as may work 
through a crack is quickly rendered harmless through reaction 
with the lime salts composing the cement. If the lining is built 
up in layers, the joint between the fresh and partially set cement is 
likely to be defective, and the crystallization of lime salts within 
the lining at this point will often cause the outer layer to loosen 
and flake off. This is avoided by grouting the plastic material 
in between the digester wall and a movable backer. 

Neither Portland cement nor any of the more complex mixtures 
which have in some cases been adopted resist entirely the action of 
the liquor. There is, moreover, a gradual erosion of the lining, 
caused by the friction of the chips and pulp. From these causes, 
and from occasional flaking off, there is always more or less of the 
cement in the pulp as discharged from the digester, but the 
particles are, in nearly every case, so heavy that passage through a 
short sand-settler is sufficient to hold them back. Such trouble 
as may be due to this cause is in large measure obviated by facing 
the lining with well baked brick or tile. 

In the selection of these bricks, attention should be had to the 
following points : They should be very hard and dense, and should 
not absorb more than 2 per cent, of their weight of water, after 
being immersed for twenty -four hours in that liquid. They should 
contain no considerable amount of iron or manganese, and should 
be hard baked and very well annealed, several brands of paving 
and other special brick which meet all these requirements are now 
made in this country. Bricks which are soft or under burned are 
very apt to split and crack under the changes of temperature to 
which they are subjected, and then to come away in the pulp. 
These troubles at their worst are slight in comparison with those 
which attend the working of lead linings, while the cheapness of 
cement linings and the readiness with which such slight repairs as 
they require may be effected are sufficient to ensure their general 
introduction. 



250 THE CHEMISTRY OF PAPER-MAKING. 

The pulp-digester invented by Messrs. Curtis and Jones, and 
first put in operation at the mill of the Howland Falls Pulp Com- 
pany, embodies several novel and valuable features, and has a 
remarkable record for durability and successful work in practice. 
The essential novelty of this apparatus is found in the lining, 
which is composed of blocks of artificial stone so shaped that they 
lock into each other when in place. This stone is preferably 
composed of Portland cement and ground glass or quartz, to which 
sometimes is added a percentage of soluble glass. The density 
and acid-resisting qualities of these materials are greatly aug- 
mented by the process to which they are subjected in the manu- 
facture of the stone. 

The objection to the continuous cement lining, applied in a 
plastic state, is that it is impossible to make the lining of uniform 
density. Hence, it is often defectively porous in spots, and thus 
liable to be permeated by the acid. This is avoided in the present 
instance by subjecting the blocks to pressure during the molding 
operation, which makes them uniformly dense and strong. The 
blocks are then exposed for a time to an atmosphere of carbonic 
acid gas, by which their power of resisting the acid and the me- 
chanical attrition of the pulp is very greatly increased. Digesters 
thus lined have been in operation for a year without showing 
appreciable signs of wear, and without entailing any expense for 
repairs. They are at the present time being rapidly introduced. 

Boiling. — In spite of the many different systems under which 
the sulphite process is worked, the process of boiling is carried on 
by all of them, with one exception, in practically the same way, so 
far as strength of liquors, temperatures, and time are concerned. 
The exception noted is found in the Mitscherlich process, which 
will for that reason be considered by itself, after taking up the 
processes in which boiling is conducted at comparatively high 
pressures and concluded in a comparatively short time. 

It is customary, in charging the digester, to fill it as completely 
as possible with the chips, since, before the full pressure is reached, 
the chips will settle sufficiently to be entirely covered with the 
liquor. The liquor should be run in as rapidly as possible ; and a 
6-inch pipe is none too large for this purpose, as much time may 
be needlessly wasted through the use of a small pipe. About 
2500 gallons of liquor is the proper amount for a digester carrying 
2 cords of chips. The strength of the liquor may vary consider- 



THE SULPHITE PROCESS. 



251 



ably, if the temperature is regulated to correspond, but, in gen- 
eral, liquor of 10° T., carrying about 3^ per cent, sulphurous acid, 
gives the most satisfactory results. It is very important that the 
pressure should not be run up too fast, and at least four hours 
should be taken in reaching full pressure. If the heating is forced 
at the commencement of the cook, the steam, striking the cold 
liquor, causes a violent hammering which may seriously strain the 
digester ; but a more serious objection is found in the effect upon 
the pulp. When the pressure is hurried, a high temperature is 
reached before the liquor has had time to penetrate to the interior 
of the chips. The wood inside is more or less burned in conse- 
quence, and the pulp is filled with chips showing a hard, red or 
brown central portion. Wherever such red chips are found in the 
pulp, the cause may be attributed to getting up pressure too fast. 
The liquor prevents the oxidation of the wood, and it is necessary 
that the wood should be thoroughly permeated before there is any 
considerable rise of temperature. The maximum pressure carried 
may range from 65 to 85 lbs., the higher pressure being only safe 
when the liquor is strong in sulphurous acid. The pressure, how- 
ever, affords a very unreliable indication of the conditions under 
which the operation is being carried on, and in all cases the main 
reliance should be placed upon the temperatures as shown by the 
thermometer. The temperature is the real factor in the disinte- 
gration of the wood, and the 
pressure carried, except so far 
as it indicates temperature, 
is of comparatively slight 
importance. It may be due 
in a large part to gas set 
free during the boiling, and 
in some cases, where much 
condensed water is formed, 
the pressure may be almost 
wholly hydrostatic. In most 
mills, the thermometer is 
placed on top of the digester, 
or in the blow-off pipe ; and, 
while in these places it may give comparative readings which are 
of value, the true temperature of the digester is probably somewhat 
higher than that shown. The proper place for the thermometer is 




Fig. 59.- 



mm 

Side Oil Bath. 



252 THE CHEMISTRY OF PAPER-MAKING. 

about one-third of the way down on the digester wall. An oil 
bath may be easily arranged there for its reception by passing a 
drop tube of bronze through the digester wall and lining, as shown 
in Fig. 59. A still better arrangement, however, is made possible 
by the recent introduction of what is known as the Standard ther- 
mometer. That portion of the instrument carrying the metallic 
spring passes through the digester wall, while the dial and pointer 
on the outside show the temperature as upon a steam gauge. By 
a slight modification this thermometer can be made to indicate 
the gas pressure in the digester as well as the temperature. It 
is only necessary to have printed on the dial the steam pressures 
corresponding to the various temperatures. The difference between 
the pressure shown on the thermometer and that shown by the 
steam gauge is due to gas. An electrical attachment may be 
applied to those thermometers, by means of which the temperature 
parried may be indicated at the office, or in any part of the mill. 
In the quick cooking processes, the best results in boiling are 
secured when the highest temperature carried is from 300° to 
312° F. 

As the boiling progresses, the effect of heat and the reactions 
going on inside the digester is to cause more or less gas to leave 
the liquor, and the amount of gas pressure increases with some 
regularity to the end of the cook. With a properly built digester 
this gas pressure is no detriment, provided the temperature is 
watched and carried to the proper point. It is the custom in most 
mills, however, to blow this gas off at intervals, which are more 
frequent in the last stages of the process. There is an impression 
in some quarters that if this is not done the gas will burn the pulp ; 
but this is quite erroneous, since it is the high temperature and 
the absence of sufficient gas which causes burning. If so much 
gas pressure is observed that blowing off becomes necessary, it 
merely proves that the liquor was too strong at the start, and that 
the manufacturer has gone to the expense of putting an unneces- 
sary amount of gas into the liquor, only, in most cases, to waste 
it in the boiling operation. 

There is also great danger, if too much gas is blown off, that the 
pulp will be burned; in fact, wherever burned pulp is obtained 
when the temperature has not been allowed to rise above 320° F., 
it may be inferred that the liquor was originally too weak or that 
too much gas was blown off. 



THE SULPHITE PROCESS. 253 

Unless, however, dry and hot steam is used, so much condensed 
water may form in the boiler, that blowing off is necessary in order 
to keep down the volume of liquor and prevent a hydrostatic 
pressure. 

We have already pointed out the great insolubility of the mono- 
sulphite of lime, as well as the fact that it is easily held in solution 
when the extra equivalent of gas necessary to form the bisulphite 
is present. Bisulphite of lime is a very unstable salt from which 
the extra equivalent of sulphurous acid may be easily driven off 
by heat, with formation of the monosulphite. As sulphite liquors 
rarely contain more than a very small percentage of sulphurous 
acid above the amount needed to form the bisulphite, it is evident 
that when, during boiling, any of this gas is blown off, an equiva- 
lent amount of monosulphite of lime is deposited in the digester, 
where it either causes trouble through rendering the pulp very 
difficult to wash, or, quite commonly, by the formation of a hard 
incrustation around or in the steam and blow-off pipes. We have 
seen the inside diameter of a 3-inch steampipe reduced by s^uch 
incrustation to less than |~inch, while elsewhere in the lower por- 
tion of the digester, the scale was f-inch thick. 

In order to lessen these difficulties, Kellner heats the bisulphite 
solution in a separate vessel, from which it is run hot into the 
digester. Much of the monosulphite is thus precipitated outside 
the boiler, and may be redissolved for further use by the sulphu- 
rous acid blown off during treatment of the wood. British patent 
No. 12,970, a.d. 1891. 

Strainers have been used in various digesters and for different 
purposes. In some cases a strainer bottom of iron covered with 
lead is placed on a slant within a foot or two of the bottom of the 
digester. In this case the digester discharges through a pipe at 
the side near the bottom, and steam is admitted under the false 
bottom. The strainer here serves to spread the steam, and is by 
some thought to secure a better circulation of the liquor, but its 
value in this position is very doubtful. In some digesters abroad 
a strainer was formerly placed inside the digester, and about one- 
quarter the way down, and the digester was only filled with chips 
up to the strainer, which carried a central piece which was 
removed during filling. The object of the strainer in this position 
was to prevent the chips from rising to the surface of the liquor, 
where they might carbonize and form black chips which seriously 



254 THE CHEMISTRY OF PAPER-MAKING. 

impaired the value of the pulp. The output of the digester was, 
however, greatly curtailed, and the black chips are now avoided 
quite as certainly by taking proper care to have sufficient liquor 
in the digester. Some form of strainer is always necessary in the 
top of the digester to prevent the pulp from being carried into the 
blow-off pipe. Sometimes a hemisphere of hard lead is burned 
to the manhole plate around the entrance to the blow-off ; while 
often instead of this a larger hemisphere rests on a ledge in the 
neck of the digester. In either case the metal of the strainer is 
punched with numerous 4-ihch holes. 

Much stress was formerly laid upon the importance of thorough 
circulation of the liquor during boiling, and various devices have 
been employed to secure this circulation ; among them may be 
mentioned the injector placed in a pipe leading from the bottom 
of the digester under a perforated false bottom, and discharging 
through the manhole plate at the top. When the injector is 
working properly, the liquor is drawn from the bottom of the 
digester, carried round through the pipe, and discharged on top 
of the pulp. We have worked digesters fitted with this appliance 
for several months without perceiving the slightest benefit from 
its use, and are satisfied that no advantage offsetting the additional 
expense is to be derived from any of the methods for securing 
circulation, such as outside pumps or vomiting pipes in the interior 
of the digester. No such devices are now, in fact, used in this 
process. 

Although it is, of course, desirable to discharge the digester as 
soon as possible after the reduction of the wood has been com- 
pleted, there is no danger of injuring the pulp through keeping 
it too long in the digester, provided always that the liquor is of 
proper strength, and that it has not been unduly weakened by 
blowing off. We have in several cases, where, owing to a break- 
down in another portion of the mill, it was inconvenient to blow 
a digester off at once, kept the digester under pressure for twenty- 
four hours or more after the cooking was completed, and in no 
case has the pulp been injured in the least, either as regards 
strength or color. 

With a working pressure of 75 lbs. and liquor carrying 3.50 per 
cent, of sulphurous acid, the best results are obtained when four 
or five hours are taken in reaching full pressure, and sixteen hours 
for the entire cook. There is considerable difference of opinion 



THE SULPHITE PROCESS. 255 

regarding the relative merits of the systems using high pressure 
for a short time, and those working at lower pressures for a longer 
time. In our opinion the disintegration of the wood is more com- 
plete, and the pulp softer and of purer quality, when the boiling 
is conducted at high temperatures, provided that the liquor is suffi- 
ciently strong to prevent burning. The use of strong liquor 
involves, however, more gas pressure, so that unless the boiling 
is carried on by the thermometer the temperatures reached may 
run lower than if a weaker liquor is employed ; and the pulp will 
consequently be harsh and imperfectly cooked, and will require, 
if subsequently bleached, a large proportion of bleaching powder. 

It would seem, on theoretical grounds, more desirable to heat the 
digester either by a steam jacket, or by coils of pipe, than with live 
steam, since in the latter case the liquor necessarily becomes much 
diluted. This condensed water introduces an uncertain factor in 
the working of the process, since its amount will necessarily vary 
from day to day with the temperature and dryness of the steam, 
and the temperature of the air outside. With proper care, how- 
ever, and especially if a non-conducting jacket is employed, these 
objections are not serious, and the greater convenience of the live 
steam has caused its general adoption. A good jacket of this 
description is made by plastering the digester over with clay mixed 
with cocoanut fibre. 

The amount of condensed water formed in a lead-lined digester 
of moderate size, or about 6| feet in diameter, during a single 
boiling is much larger than it would be at first sight supposed. 
Under ordinary conditions, in summer, we have found this amount 
to be as large as 1000 gallons, and during the cold winter of the 
Northwest we have frequently known the amount to be so great 
as completely to fill the digester. In such cases it is, of course, 
impossible to heat the liquor by any further addition of steam, and 
the cook can only be completed by allowing the pressure to fall 
until most of the dilute liquor can be run off, and then making a 
fresh start with new liquor. The advantage of the thermometer 
is very apparent in a case like this, as when the digester is filled 
with water the pressure remains at the proper point, and the true 
condition of affairs is only shown by the steady dropping of the 
temperature. In the case mentioned above the mill was practically 
heated by radiation from the digesters, and the trouble was over- 
come by boxing them in so that they were shut off from the rest 



256 THE CHEMISTRY OF PAPER-MAKING. 

of the mill. If the liquor has been unduly weakened by the con- 
densed water, although not necessarily to the point indicated 
above, the fact may usually be ascertained by the raw and chippy 
condition of the pulp. 

The introduction of cement linings has practically eliminated 
the difficulties due to condensed water and loss of heat through 
the digester wall. Considerable condensed water is, of course, 
still formed, and there is still some loss of heat by radiation, but 
both factors are by these linings greatly reduced in value, and, 
which is of far more importance, they are made to have a nearly 
uniform value for each cook. 

It is desirable to have the connections between the generating 
boilers and the digesters as short as possible, to avoid loss from 
condensation of steam and reduction of the steam pressure. Where 
a number of digesters are fed from the same steam-pipe, its area 
should be several times greater than that of all the pipes leading 
from it, or else, as our tests in practice have shown, the digesters 
at the farther end of the pipe will receive steam under Considerably 
lower pressure than those nearer the boilers. All steam-pipes 
should be well trapped, and steam as dry as possible should be 
used for cooking, in order to keep down condensed water. 

The steam-pipe leading into the digester is often led up to the 
top of the digester, and then back and into the bottom, to form a 
trap, and is fitted with two check- valves, — one placed on the 
horizontal arm of the steam-pipe, near the digester, and the other 
on the vertical arm of the trap. The object of these precautions 
is to prevent any of the liquor from being forced from the digester 
into the generating boilers, as may easily happen if the gas pressure 
is considerable in the digester, when, for any cause, the steam 
pressure has been allowed to fall in the boilers. Considerable 
danger to the boilers may be apprehended, if the liquor finds its 
way into them, as the acid rapidly attacks the iron, while the 
sulphite of lime is likely to form scale. 

Boiling by the Mitscherlich Process. — After the digester has 
been packed with chips or blocks, which are levelled off, so that 
none shall be uncovered by the liquor, wet steam is admitted into 
the boiler, and the steaming continued from eight to twelve hours. 
Care is taken to avoid any pressure in the boiler, as, if the tem- 
perature is allowed to rise above 102°, the wood is in danger of 
burning. The water, condensing, flows away as brown liquor. 



THE SULPHITE PROCESS. 257 

The object of the steaming, and subsequent admission of cold 
liquor, is to bring the liquor, at the start, well into the pores of 
the wood, so as to prevent floating and burning. 

The liquor used stands from 5°-7° Be. ; and after the steaming 
is finished, this is drawn into the digester by the partial vacuum 
which forms as the digester cools, and more rapidly as the cold 
liquor is injected. The flow of liquor is continued until it comes 
to within about 15 inches of the top of the digester. Steam is 
then admitted into the lead coils, and the temperature of the 
digester contents is brought to 110° C. in as short a time as may 
be, although, on account of the large size of the digester, this may 
require twelve hours or more. This temperature is maintained for 
about twelve hours, and is then gradually increased to 117°-120° C. 
The pressure on the digester should, according to Mitscherlich, 
be at no time allowed to exceed 45 lbs. The quantity of gas 
blown off, and the length of the boiling operation, is governed by 
tests made upon samples of liquor taken from the digester. For 
these tests, tubes are used which are 200 mm. long, closed at one 
end, and graduated into |-, T 2 g, g 1 ^, and g 1 ^ of their length. A 
mixture of strong ammonia and water in equal parts is poured 
into the tube up to the -^ mark, and the balance of the tube is 
filled with liquor, and the tube well shaken. 

All the bisulphite of lime present is thus converted into mono- 
sulphite, and precipitated ; and from the volume and character 
of precipitate, conclusions as to the progress of the operation are 
drawn. The higher the precipitate stands in the tube, the more 
bisulphite there is in the liquor. The liquor grows darker as the 
cooking is prolonged, and the precipitate, which is at first light 
and fine, becomes coarse, and settles rapidly. When, after a few 
moments' standing, the precipitate fills only -^ the length of the 
tube, gas is blown off from the digester in moderate quantity, and 
at ^j the amount blown off is increased sufficiently to bring- a tem- 
perature down to 110°. The completion of the cook is indicated 
when the precipitate sinks to g 1 ^. 

The course of a Mitscherlich cook and the very long time 
required to carry it through are well brought out in the following 
tables from Schubert. 1 It will be noticed that the total time of 
boiling is reckoned from the commencement of what is taken as 
the first stage of the pulping operation ; i.e. from the time of reach - 
1 Die Cellulosefabrikation. 



258 



THE CHEMISTRY OF PAPER-MAKING. 



ing 108°. For any comparison with a quick cook the time taken 
to reach this temperature should, of course, be added to the so- 
called total time as given. 



Boiling No. 207. - 


— In a 


Horizontal 


Digester. 






Pressure in atmospher 


es. 


Teruperatur 


April 23. 


11.30 A.M. 




0.00 




45 




8 P.M. 




0.60 




72 


April 24. 


1 A.M. 




0.75 




85 




6 




1.00 




96 




11.30 




1.50 




105 




2.30 p.m. 




1.75 




108 




6.30 




2.00 




112 


April 25. 


1 A.M. 




2.50 




115 




6 




2.80 




116.5 




9 




3.00 




119 




12 M. 




2.80 




120 




3 P.M. 




2.25 




119 




10 




2.10 




118 



Remarks. 
Filled April 22, from 1.30 to 11 p.m., 88 cubic metres wood in disks, 
9 cubic metres wood in chips. 

Steamed from midnight to 8 a.m. April 23. 
Acid of 5° Be. run in from 8 to 11.30 a.m. 

After 27 hours temperature reached 108° 
After 48.5 hours temperature reached 116° ) "> 
After 58.5 hours boiling finished at 118° ) 

Total time of boiling: 31.5 hours. 



21.5 hours. 
10. hours. 



Highest pressure, 3 atmospheres. 
Cellulose, very fair. 



Highest temperature, 120°. 



Boiling No. 


20. 


— In 


A 


Horizontal 


Digester. 










Pressure 


in atmospheres. Temperature, °C. 


le 2. 


6 A.M. 
11 
4 P.M. 

12 










0.0 
0.5 
1.0 
2.0 


40 

73 
97 

108 


le 3. 


5 A.M. 

7 
12 m. 

10 P.M. 










2.7 
3.0 
3.0 
3.0 


116 
118 
118 
118 


le 4. 


8 A.M. 
1 P.M. 










3.0 
3.0 


118 
118 



THE SULPHITE PROCESS. 



259 



Remarks. 

Filled June 1, 1 p.m. to 3.30 a.m., with 60 cubic metres of wood. 

Steamed from 3.30 a.m. to 3.30 p.m. June 2. 

Liquor of 5.5° Be. pumped in from 4.30 p.m. to 6 a.m. 

After 18 hours reached 108° 

After 25 hours reached 118° 

After 55 hours finished at 118° 
Total time of boiling . . 
Cellulose, good. 






7 hours. 
30 hours. 

37 hours. 



Boiling No. 101. — In an Upright Digester. 









Pressure in atmospheres. 
At top. At bottom. 


Temperature, °C. 
At top. At bottom. 


Aug. 


2. 4.30 


P.M. 


0.0 


0.0 


30 


40 


Aug. 


3. 9 


A.M. 


0.3 


0.3 


87 


87 




11 




0.4 


0.3 


89 


89 




1 


P.M. 


1.0 


0.4 


96 


95 




3 




1.2 


1.0 


102 


99 




6 




1.3 


1.2 


106 


103 


Aug. 


4. 6 


A.M. 


2.4 


2.3 


120 


115 




8 




2.4 


2.3 


122 


116 




10 




3.0 


2.4 


122 


117 




12 


M. 


3.0 


2.4 


122 


117 




2 


P.M. 


3.0 


2.4 


122 


117 




4 




3.0 


3.0 


122 


117 




6 




3.0 


3.0 


122 


117 


Aug. 


5. 6 


A.M. 


3.0 


3.0 


122 


117 




7.30 


i 


3.0 


3.0 


122 


117 



Remarks. 

Filled Aug. 1, p.m., with wood of mixed sizes. 

Steamed Aug. 2, from 1 a.m. to 1 p.m. 

Liquor of 5-|° Be. pumped in from 2.15 to 4.15 p.m. 
After 28 hours reached 108° ^ 
After 30 hours reached 114° >- 9 hours. 
After 37 hours reached 118° ) \ 
After 63 hours finished at 118° ) _ 0UrS - 
Total time of boiling . . 35 hours. 

Emptied on morning of Aug. 6. 
Cellulose, fine. 

This boiler was 4 metres diameter, and 9 metres high ; and contained 
60 cubic metres of wood in disks. 



260 THE CHEMISTRY OF PAPER-MAKING. 

It was formerly considered established as a fundamental law in 
this process, that the pressure in the digester should never exceed 
45 lbs., and if a temperature of 114° was reached, gas was at once 
blown off. Now, however, the boiling operation is shortened as 
much as possible, and by bringing the pressure from 3.4 to 3.5 
atmospheres, and the temperature to 120° C, no evil results are 
experienced, and the time is cut from seventy-five to eighty-five 
hours down to fifty-eight hours or less ; of which only thirty-two 
are properly consumed by the boiling. It is usual in Germany 
to hold the pressure up to the very end, and in this country it is 
often slowly and regularly raised during the last hours. 

The body of pulp contained in one of these digesters is so great 
that there is danger of burning as soon as the liquor has been run 
off, and it is therefore customary to let in cold water and wash the 
pulp two or three times in the digester. Even then the pulp is 
still so hot that all manholes are opened, and holes punched up 
through the stuff to create a draft of air. The pulp is finally 
shovelled out of the digester. 

The actual time consumed by one cook from the time of filling to 
that of blowing off is, as shown by the tables previously given : — 

No. 20 80| hours. 

101 87 

207 72 

In addition to this the time required for discharging the liquor, 
cooling, washing, emptying, and for repairs, is at least from 
eighteen to twenty-four hours, making a grand total of ninety to 
one hundred hours, and allowing only seven or eight cooks per 
month at best. 

It is customary after each boiling by the Mitscherlich process 
to inspect the digester for the location of any leaks or weak places 
in the cement. Such affected portions may, in most cases, be 
quickly repaired by cutting out the cement and repointing. A 
considerable incrustation of sulphite of lime forms on the lead 
coils during each cook, and is usually removed by rapping with 
a mallet. This is likely to dent the pipes, and a better way is to 
use a scraper. Any leaks in the coils cause trouble through depo- 
sition of sulphite within the pipe. A stream of weak hydrochloric 
acid sent through the coil will remove this, unless the deposit at 
any point is sufficient to close the coils. 



THE SULPHITE PBOCESS. 261 

The standard Mitscherlich digesters with 40 x 14 shell carry 
from 22 to 25 cords of wood at a charge, and yield from 10 to 14 
tons of fibre at a boiling. So much time is lost, however, in wash- 
ing, emptying, and charging up, that these digesters rarely show 
in continuous working a better average output than 3000 lbs. per 
twenty-four hours. 

Leaving breakdowns out of account, there is hardly an excuse 
when good pulp has once been made by any process, and the con- 
ditions governing that boiling are fully known, for failure to 
produce pulp of similar quality, since the same conditions must 
invariably produce the same results. The trouble usually arises 
from imperfect knowledge of the conditions, and every care should 
be taken to learn and govern them as accurately as possible. A 
few of the first importance may be pointed out. It is absolutely 
necessary, in order to obtain pulp of uniform quality, to use with 
the same kind of wood liquor of good and always uniform quality. 
There should be no variation in the time taken for reaching pres- 
sure, or in that during which the pressure is maintained ; the con- 
densed water and consequent dilution of the liquor should be kept 
at a definite and regular amount by preventing radiation as much 
as possible, and by using steam of uniform pressure. The amount 
of gas blown off, if any, must also be controlled, and should not 
vary from day to day. Failure to make good pulp usually results 
from disregard of these conditions, which can all be readily con- 
trolled. There are certain others which necessarily introduce 
some uncertainty in the process ; one of these is the variation in 
the condition and moisture of the wood used. 

Recovery of Gas. — At the time of the present writing, 1893, 
no attempt is made in any mill in this country other than those 
working the Mitscherlich process, to recover the large proportion 
of sulphurous acid which is blown off previous to the dumping of 
the digester, although the gas may be utilized by a very simple 
apparatus, which is regularly in use abroad. The best form of 
apparatus for this purpose consists of a tower filled with flints or 
broken brick. The gas and steam from the blow-off are admitted 
to the tower under the false bottom, while a shower of water is 
kept up at the top of the tower. This water, as it passes down 
the. tower, absorbs the gas and is somewhat heated by the steam ; 
as it progresses, more gas is absorbed until the water becomes 
saturated, while through condensation of the steam the tempera- 



262 



THE CHEMISTRY OF PAPER-MAKING 



tarre of the water is soon raised to a point where it can no longer 
hold the gas in solution. This liberated gas, passing upward with 
that still coming from the digester, soon increases in quantity to 
such an extent that the water falling down is not sufficient to dis- 
solve it, and there is constantly delivered from the top of the 
tower a stream of pure gas, while from the bottom of the tower 
hot water is drawn, to be used in washing or for other purposes. 
The amount of sulphur thus saved is usually not less than 20 per 
cent. 

In the Mitscherlich process the waste gases are blown through 
a pipe leading from one of the upper manhole plates to a lead coil 
immersed in water. All the digesters are connected with this 
coil, which in turn is connected to one of the towers. The steam 
carried over by the gas is condensed and the pure gas passes on 
into the tower. Such recovered gas, being undiluted with atmos- 
pheric nitrogen, is better suited for the preparation of strong 
liquors than the original furnace gas. It may be made to yield 
a liquor standing 12° Be*. 

Dr. Kellner has also used the coil and tower for recovering the 
gas blown off during the cook. For recovering that discharged 




Fig. 60. — Kellner Recovery Apparatus. 

with the liquor after the cook is finished, he has employed the 
apparatus shown in a diagrammatic way in Fig. 60. 

At Northfleet, England, the simple plan is adopted of blowing 
off the gas into a six-inch pipe laid on the ground, and leading to 



THE SULPHITE PROCESS. 



263 



the tower. The pipe has a pitch toward the mill, and the con- 
densed water flows back, while the gas goes forward. 

Various means are adopted in the different mills to get the pulp 
out of the digester. That which now finds most favor is to blow it 
out under a pressure of about 30 lbs. The digester is thus emptied 
perfectly clean in a few seconds, and the pulp is so well disin- 
tegrated that no subsequent treatment in the beating engine is 
necessary to fit it for the market. It is urged against this method, 
that there is danger of breaking up the knots and uncooked chips, 
thus causing shive and dirt, while at the same time unnecessarily 
straining the digester. The danger to the digester is practically 
nothing, and there is certainly less danger of breaking up the 
knots in this way than by running the pulp for several hours 
under the roll of the beating engine. Where the pulp is simply 
allowed to run out of the digester, considerable time is lost, and a 
large amount of water 



D 




must be pumped into the 
digester before the pulp 
is all out. This water is 
in most cases cold, and 
the sudden admission of 
it in so large a volume 
strains the lead severely. 
The practice of washing 
the pulp in the digester 
before discharging must 
be condemned, as the 
whole product of the mill 
is curtailed, while an 
expensive piece of appa- 
ratus is employed in 
doing work which can 
be much more efficiently / 
done in apparatus costing 
only a fraction as much. 

The Mitscherlich 
stamping mill, as used in 
foreign mills, is shown in 
side view and sections in Figs. 61 and 62 ; on about seven 
of the frames A is laid or carried the shaft B, bearing numer- 




MlTSCHERLICH STAMP MlLL. 



264 



THE CHEMISTRY OF PAPER-MAKING. 



cms cams ; the shaft turns about ten times in a minute ; there 
are two stout beams, D D' and C, which hold the frames 
together, and also serve as guides for about 60 stamps, which 
reach nearly to the bottom of the stamping trough E; the trough 
is 15 metres long, and rises about 0.6 metres in this distance ; the 
stamps are lifted by teeth, which engage the cams ; the teeth of the 
three or four adjacent stamps are arranged as in Fig. 61, so that 
these stamps, instead of falling together, follow each other. This 

action, and the flow of 
water through the trough, 
passes the stuff along ; 
the action of the mill is 
largely a rubbing one, on 
account of the different 
motion of the adjacent 
stamps : in some mills 
the wood is broken up by 
a heavier stamping ma- 
chine before boiling. This 
saves subsequent stamp- 
ing, and makes somewhat 
shorter cooks possible. 
The stuff is also worked 
under edged runners, and 
these are commonly em- 
ployed to reduce knots 
and chips to a pulp suit- 
able for coarse papers. The unreduced remainder is roughly 
screened from the fibre by rotating drums similar to rag dusters. 

If the digester has been blown off into a drainer, the most con- 
venient method of washing the pulp is to flood it two or three times 
with water. It should be observed, however, that the pulp forms 
in itself a most efficient filter, so that, in case the wash water 
carries any considerable amount of suspended organic matter, this 
will be fixed upon the pulp, and more will be lost than gained by 
prolonging the washing. In some mills the washed pulp is trans- 
ferred, with little labor, from the drainer to the chest, in readiness 
for the wet machine, by directing a powerful stream of water 
against the mass of pulp in the drainer, and washing it out in a 
sluiceway, from which a pump throws it over into the chest. In 




Fig. 62. — Mitscherlich Stamp Mill. 



THE SULPHITE PBOCESS. 265 

other mills the drainers themselves consist merely of large chests 
with a wooden chimney for the escape of gas, and an agitator. 
In this case no attempt is made to wash the pulp in the drainer, 
but it is pumped direct into the washing-machine. The drainers 
should always be protected before blowing off, by a foot or two of 
water let into the bottom, to break the force of the pulp as it 
strikes the drainer bottom. 

The washing-machine just referred to, although not in common 
use, is very efficient, and consists merely of a trough provided with 
three or four washing cylinders, with a corresponding number of 
back-falls. The first cylinder removes a large proportion of the 
water from the pulp, and, as the pulp is thrown over the back-fall, 
it meets a copious stream of fresh water from a pipe behind the 
washer ; and the same operation is repeated as many times as 
there are washers while the pump passes along the trough. 

Washing in the engine is conducted after the ordinary method, 
which is too well known to require comment further than to point 
out the great danger of breaking up chips and forming shive, 
unless the engine roll is well raised. 

Thorough washing, although always desirable, must be insisted 
upon wherever the pulp is to be bleached; for monosulphite of 
lime requires a large amount of water for its complete removal, 
and, if present in the pulp, may greatly increase the consumption 
of bleaching powder, as it is one of the most efficient antichlors in 
use. When present in excessive quantity, it may be best removed, 
and the pulp considerably benefited, by washing with dilute 
hydrochloric acid. 

The further handling of the unbleached pulp belongs to the 
practical paper-maker rather than to the chemist. 

The bleaching of this pulp and of the other paper-making fibres 
will be considered in a separate chapter ; but we may here point 
out that it is desirable, before bleaching sulphite pulp, to remove 
all large shives by thorough screening, as, in the bleaching 
process, these shives are broken up into smaller ones, which it is 
very difficult to remove, and which injure the appearance of the 
paper, though they may readily escape notice in the wet pulp. 

Well cooked and bleached sulphite pulp should be soft, strong, 
and of pure color ; the frequent failures to meet these require- 
ments are due either to imperfect cooking, which leaves the pulp 
harsh and hard, or to defects in the method of bleaching, which, 



266 THE CHEMISTBY OF PAPER-MAKING. 

especially when hot bleach is used, may lower the color and injure 
the strength, by chlorination and oxidation of the fibre. 

The conditions which affect unfavorably the quality of the 
finished pulp have been already pointed out in some instances, but 
may be conveniently considered together. Poor color may be due 
to imperfect cooking, which has failed to remove the necessary 
amount of incrusting matter, or it may be caused by unduly 
weakening the liquor by blowing off too much gas. If the proper 
cooking temperatures are maintained the color of the pulp improves 
as more gas is present in the liquor. Raw pulp is, of course, due 
either to insufficient time or too low a temperature, and the latter 
may be caused by working with too strong a liquor, in which case 
the large amount of gas pressure makes it difficult to bring up the 
temperature to the proper point ; or, if very wet steam is used, or 
if the digesters radiate an undue amount of heat, the quantity of 
condensed water formed in the quick cooking digesters may be 
sufficient to fill the digester and prevent the admission of the 
necessary steam. Black chips similar to charcoal are found in the 
pulp when any of the wood has remained uncovered by the liquor, 
and a simple remedy for them is found in more liquor or less wood. 
If the whole body of the pulp is burned, it means that the liquor 
was too weak for the temperatures carried. If too much gas is 
blown off the liquor may be weakened during the boiling to an 
extent which permits the pulp to .burn, and burning is especially 
likely to occur if the liquor is drained off and the cooked pulp 
allowed to remain in the hot digester for more than a few moments 
before water is run in. After the pulp has been cooked, it may be 
kept in the digester under pressure for almost any length of time, 
if the liquor contains a good supply of gas. Chips which are well 
cooked upon the outside, but which have a hard, red or brown 
centre, are formed when the temperature has been raised so rapidly 
that the liquor did not have time to penetrate into and protect the 
interior of the wood before the temperature was high enough to 
burn such unprotected portions. Any great precipitation of mono- 
sulphite of lime in the pulp, where it makes trouble by causing 
specks, is due either to the use of a liquor containing little or no 
free sulphurous acid above that needed to form bisulphite, or else 
to the formation of such a liquor in the digester, by blowing . off too 
much gas. The objectionable red coloration which some sulphite 
pulp takes on after washing is the result, so nearly as we can 



THE SULPHITE PROCESS. 267 

determine, of the oxidation of portions of incrusting matter, which 
have not been removed during cooking, and can generally be 
avoided when the cooking is made more thorough. Strangely 
enough, however, the pulp from poplar wood, which is very easily 
reduced by the sulphite process, frequently develops this color in a 
way much more marked than spruce. The color is a purer one, 
and often approaches a delicate pink. Dirt and specks, of course, 
find their way into the pulp from various sources. Fragments of 
bark which have not been removed in the preparation of the wood, 
fragments of knots which have been broken up by the boring 
machine or in the treatment of the pulp subsequent to boiling, and 
shives formed by the breaking up of uncooked or partially burned 
chips, are the most common causes of dirt, but lumps of mono- 
sulphide left by imperfect washing, iron scale from water pipes, 
sulphide of copper from pipes and fittings, coal, black sand, and 
fragments of brick, all frequently find their way into the product. 

The unbleached sulphite fibre, owing to the numerous systems 
employed for its production, shows even wider variation in quality 
than the bleached fibre. As found in the market, it may be either 
a harsh and somewhat transparent very strong fibre, or one nearly 
as soft and white as the bleached pulp. Spruce is the wood most 
preferred in this country for making this pulp : abroad, the Swedish 
fir and pine are both used, as well as spruce, and several of our 
common woods readily yield a strong fibre. We give below a very 
complete analysis, made by ourselves, of a sample of sulphite fibre 
made from spruce by the Mitscherlich process. 

Analysis of Unbleached Sulphite Pulp. 

(Mitscherlich Process.) 

Per cent. 

Moisture, loss at 100° C 9.000 

Extractive organic matter, soluble in very dilute 

hydrochloric acid 0.516 

Extractive organic matter, soluble in very dilute 

alkali 1.505 

Eesin 0.060 

Cellulose -. 80.800 

Mineral matter: 

a. Eemovable by very dilute acid ...... 0.758 

b. Not removable by very dilute acid . .... 0.742 
Lignin, by difference . - . . • 6.619 

100.000 



268 



THE CHEMISTRY OF PAPEB-MAKING. 



Mineral matter : 

a. contains — p er cent. 

Silica (Si0 2 ) i . 0.009 

Iron sesquioxide (Fe 2 3 ) 0.031 

Sulphate of lime (CaS0 4 ) 0.333 

Sulphite of lime (CaS0 3 ) 0.004 

Carbonate of lime (CaC0 3 ) 0.261 

Carbonate of magnesia (MgC0 3 ) 0.025 

Carbonate of soda (Na 2 C0 8 ) 0.095 

0.758 

b. Ash of washed pulp contains — Per cent. 

Silicate of soda (Na 2 Si0 3 ) . 0.042 

Iron sesquioxide (Fe 2 3 ) 0.010 

Sulphate of lime (CaS0 4 ) 0.158 

Carbonate of lime (CaC0 3 ) . 0.050 

Carbonate of magnesia (MgC0 3 ) ...... 0.029 

Carbonate of soda (ISra 2 C0 3 ) . . 0.453 

0.742 

Total mineral matter in sample 1.500 

Oxygen and carbonic acid lost on burning (calcu- 
lated) 0.398 

Calculated ash to be obtained from sample .... 1.102 
Actual ash obtained by burning 1.084 

Our analyses in the following table, although much less com- 
plete than the one given above, will serve to point out the varia- 
tions in quality likely to be found in unbleached sulphite fibre. 
They are all of pulp made from spruce wood. 

Analyses of Unbleached Spruce Sulphite Fibre. 
(Quick Cooking Process.) 



Moisture, loss at 100° C 

Mineral matter (ash) ....... 

Hydrocellulose, etc. (soluble in alkali) . 

Cellulose 

Non-cellulose ("lignin") by difference 



6.15 


6.70 


6.57 


1.00 


0.45 


0.33 


2.53 


2.26 


4.25 


85.32 


89.74 


88.12 


5.01 


0.85 


0.73 



6.45 

0.65 

1.52 

81.51 

9.87 



In studying these analyses, it will be noticed that the propor- 
tions of cellulose and of the incrusting matter remaining with it 
vary greatly in the different samples. This is a point of much 



THE SULPHITE PROCESS. 



269 



practical importance, especially when the pulp is to be bleached, 

since all this incrusting matter must be destroyed by the bleaching 

powder. If the incrusting 

matter is present in large 

amount, the consumption of 

bleach becomes excessive, 

and the pulp shows great 

shrinkage. 

We have made in our 
laboratory a large number 
of determinations showing 
the yield and character of 
pulp obtained by the sul- 
phite process from different 
wood. In these experiments 
we have used a digester 
(Fig. 63) built of bronze, 
lead-lined, and holding 
about 12 litres. A drop 
tube, passing from the top 
nearly to the bottom of 
the digester, was utilized 
as an oil bath for carry- 
ing the thermometer, while 
pressures were shown upon 
an ordinary gauge. 

The accompanying table 
gives the results of these experiments. The figures give the per 
cent, of fibre obtained from the dry wood. 

Spruce . .' 50.75 

Poplar 55.18 

Cottonwood 50.80 

Gum 45.73 

Beech ............. 42.80 

Birch 53.80 

Maple 52.61 

Fungoid Growth on Fibre. — The black specks having the 
appearance of mildew, and which sometimes appear on unbleached 
fibre which is stored for a considerable length of time when in 




Fig. 63. — Experimental Digester. 



270 THE CHEMISTRY OF PAPER-MAKING. 



moist condition, have been carefully studied by Herzberg, whose 
examination proves them to be due to a fungoid growth upon 
the fibre. The sample of pulp examined was prepared by the 
Ritter-Kellner process, and was disfigured by numerous black 
spots, varying in size from that of a pin head to that of a pea. 

The appearance was quite different from that occurring in straw 
cellulose which has been stored in damp places. Microscopical 
examinations demonstrated the existence of a fungoid growth, 
twining around the cellulose fibres as ivy does around a tree. The 
brown color of its mycelium caused the patches of it to be visible 
to the naked eye as dark specks. It was thought that the germs 
had been derived from the river water used in the manufacture, 
spring water not being available, but it is more likely that they 
came from the air, finding a good soil on the moist cellulose. 

Calcium sulphite was recognized on the spots by Frank's method 
with iodine solution, and if this be viewed as the cause of the 
growth, the obvious remedy is to avoid its presence in the finished 
product ; on the other hand, the acid juices of the growth itself 
will tend to liberate sulphurous acid from the calcium sulphite, 
and arrest its development. Thorough drying is an efficient pre- 
ventative, and where this is impracticable the use of a very weak 
solution of zinc chloride is said to act as a reliable antiseptic in 
killing the germs. 

It was observed that a paper made from pure rags and highly 
sized with rosin developed a fungoid growth when kept in a warm, 
damp place. There is no direct evidence to show whether the 
germs are derived from the water or air. Adequate nutriment for 
the mould is supplied by size of animal origin, and even when 
rosin is used the accompanying starch may prove sufficient. 

The Waste Liquor. — The waste liquors from a well-conducted 
sulphite boiling are of a light golden-brown color, and contain, in 
solution, or in combination with the bisulphite, about 50 per cent, 
of the weight of the dry wood. If lime is added to such liquors, 
a considerable portion of this organic matter is thrown down, and 
monosulphite of lime produced. The addition of a soluble alkali 
like soda determines the precipitation of the organic matter in 
brown flocks. On account of the action of the sulphurous acid 
in preventing oxidation, the organic matter in the solution has 
not undergone great chemical change, but exists in somewhat the 
same condition, as far as its chemical relations are concerned, as 



THE SULPHITE PROCESS. 271 

in the incrusting matter of the wood, and it is probable that, with 
the further development of the sulphite process, methods will be 
worked out by which this large amount of waste material may 
be utilized. The most obvious direction for such methods to take 
will be toward the preparation of glucose, alcohol, and oxalic and 
pyroligneous acids, since well-known processes are now in opera- 
tion for making these compounds from similar materials. 

The waste sulphite liquors have been found to contain, besides 
calcium sulphite and sulphate, mannose, galactose, and vanillin, 
and to yield, upon distillation with sulphuric or hydrochloric acid, 
furfurol or furfuramide, proving that pentaglucoses are present. 
Of these xylose * has been found. 

According to Cross and Bevan, the double compounds of the 
aldehydes and bisulphites in the waste liquor are not broken up 
by dialysis, and are precipitated unchanged by alcohol, or alcohol 
and ether. 

Mitscherlich has shown that there exists in the solution a com- 
pound apparently similar to tannin, at least so far as its power 
to precipitate glue goes, and he has based upon this fact a method 
involving the use of spent sulphite liquors in sizing paper. In 
Germany the farmers in the neighborhood of the sulphite mills 
find that the waste liquors are of considerable value in preventing 
the escape of ammonia when sprinkled upon compost heaps. 

Dr. W. Buddeus, in the Papier-Zeitung of March 19, 1891, has 
an interesting summary of the results obtained by an investigation 
of the composition of the waste liquor and the substances derived 
therefrom. We give his results somewhat in detail : — 

The waste liquor was neutralized with ammonia, the lime was 
precipitated by ammonium carbonate, and the carbonate of lime 
thus formed was separated by filtration. The dark brown filtrate 
was evaporated, and the dried residue distilled. The residue con- 
tained 7.2 per cent, ammonia as salts. Water and a yellow-colored 
oil were obtained in the condenser, and finally a crystalline subli- 
mate appeared on the walls of the tube. The gases escaping were 
caught in the gasometer. The oil, at first, had an odor like mer- 
captan, but this disappeared on heating slightly. This odor was, 
without doubt, due to organic sulphur compounds which were 
present in traces. The oil and water were, after this heating, 

1 Xylose, the sugar of wood, melts at 144° C, and Is dextro-rotary. Upon boiling 
with dilute sulphuric acid, it yields wood gum. 



272 THE CHEMISTRY OF PAPEB-MAKING. 

distilled with steam. The distillate was shaken out with ether, 
then dried, and the ether evaporated over calcium chloride. A 
brown oil remained, which boiled at 130° C, and which colored 
a fine chip, moistened with hydrochloric acid, a strong carmine, 
and which was therefore believed to be pyrrol. Pyrocatechin was 
also obtained in the distillate, as was proved by color-tests with 
iron salts, and its reduction of Fehling's solution. 

The gases were carbon moxide, hydrogen, marsh gas, and sul- 
phureted hydrogen. 400 grammes of the residue yielded 180 
grammes of coke, 30 litres of gas, and 200 grammes of distillate. 

Mucic and saccharic acid could not have been present as such 
in the liquor, because they are formed by the oxidation of carbo- 
hydrates, and the action of the liquor is a reducing one. Pyrrol 
is formed by the distillation of ammonium salts of these two acids. 
The only way of accounting for pyrrol is the presence of succinic 
acid, which is very probably present owing to the occurrence of 
resins in the wood. Ammonium succinate changes readily by 
splitting off of water into ammonia succinamide, which by heating 
with reducing agents gives pyrrol. 

The presence of pyrocatechin is due to that of dioxybenzoic acid 
(1, 3, 4), which is in the liquor as dipyrocatechuic acid. The 
decomposition of this by distillation with ammonia is a source 
of tannic acid and pyrocatechin. There is, according to Dr. 
Buddeus, no tannic acid present in the liquor, which will give 
a blue-black color with ferric chloride, because the tannin in wood 
is reduced by cooking with sulphurous acid. The reduction is 
probably to dipyrocatechuic acid, but by treating with ammonia 
and distilling, tannic acid is eventually formed. Sulphites are 
oxidized to sulphates when the tannin is reduced. It may be, 
therefore, that the difficulty of pulping wood rich in tannin by 
the sulphite process is due to the action of the tannin, which 
renders the sulphurous acid ineffective. 

According to Schubert, the greatest difficulty with which Ger- 
man manufacturers of sulphite pulp have to contend, is found 
in the disposal of the waste liquor and wash waters. The laws 
there are far more stringent than in this country in respect to the 
pollution of streams, and the number of water-courses of consider- 
able size is also comparatively small. No practical method is 
known for eliminating the sulphurous acid and organic matter 
in the waste liquor. 



THE SULPHITE PROCESS. 273 

The evaporation of the liquor offers no solution of the difficulty, 
and the product is of absolutely no value as fuel. The waste 
liquors are in Germany often run off in open liquor ponds, where 
they are allowed to soak in the ground. These ponds in time 
develop a very unpleasant odor and seriously contaminate the 
wells of the neighborhood. The impure wash waters, when 
allowed to run in small streams, set up conditions which seem 
peculiarly adapted to the growth of algse. 

According to the experiments of Dr. Weigelt-Reufach, liquors 
containing from 0.6 to 0.75 per cent of sulphurous acid require 
dilution with fifteen hundred times their volume of water in order 
to render them harmless to fish and other forms of animal life. 
The action of the sulphurous acid is, of course, to lower in the 
water the proportion of dissolved oxygen which the fish cannot 
breathe. The precipitated resins and gummy matters are them- 
selves injurious, not so much on account of any poisonous quality, 
as of their action in coating over the gills and shutting off the 
supply of oxygen, as pointed out by Dr. Frank. 

It is of course evident that nearly as much material from the 
wood is carried away in the waste liquors as is obtained as pulp, 
and the quantity of organic matter thus discharged by a large mill 
is therefore very great. The waste liquor from a Mitscherlich 
boiling contained per litre, — 

Sulphurous acid 3.86 grammes, 

Sulphuric acid 7.33 •" 

Chlorine 0.29 " 

and by evaporation of one litre, and drying at 110° C, yielded 
109 grammes of residue, which on ignition left 19 grammes of ash 
containing, — 

Sesquioxide of iron 0.02 grammes. 

Lime 10.30 " 

Magnesia 0.30 " 

Potash 0.28 " 

Soda 0.10 " 

11.00 grammes. 

There were, therefore, in the liquor 90 grammes of organic 
matter per litre, or 90 kilogrammes per cubic metre, or 5400 kilo- 
grammes per charge of 60 cubic metres. 

Traces of sulphurous acid gas are almost constantly present in 



274 THE CHEMISTRY OF PAPER-MAKING. 

the atmosphere within or immediately around a sulphite mill, and 
where apparatus or methods are defective the proportion of gas 
is likely to be so great as to become a source of much annoyance. 
Even small quantities of the gas produce, when inhaled, consider- 
able irritation of the mucous membrane of the throat and lungs. 
In consequence of this irritation the tendency to take cold is 
increased, and if the irritation persists, a chronic cough or bronchi- 
tis may be established. The effects of the gas upon plants and 
animals have been carefully studied by numerous observers, whose 
conclusions are by no means in harmony with each other. There 
seems to Ibe no doubt, however, that even small proportions of the 
gas are injurious to both animals and plants, but we are inclined 
to think that much of the ill effect which has been charged to the 
gas alone has been caused by the practice, which was at one time 
common, of blowing the digesters off into the open air, so that all 
the neighboring vegetation was covered with a film of condensed 
liquor in which free sulphuric acid was afterwards developed by oxi- 
dation. This practice is now happily done away with everywhere. 

According to Schroeder both deciduous and evergreen trees 
absorb sulphurous acid through their leaves from air containing 
as little as one five-thousandfrh of the gas by volume. The leaves 
retain it mostly, but a small portion penetrates into the leaf stalks 
and bark, where it may be found either as sulphurous or sulphuric 
acid. Evergreen trees are less sensitive in this respect than others. 

Stockhart finds that a distance of 630 metres is sufficient to 
protect all vegetation if the vapors, even in large quantity, escape 
from a chimney 82 feet high. 

Dr. Ogata has made a series of experiments on animals in Pet- 
tenkofer's laboratory. He finds that different animals differ greatly 
in their susceptibility to the action of the gas ; frogs being most 
sensitive, then mice, rabbits, and guinea pigs, in the order named. 
As little as 0.04 per cent, affected all the animals mentioned. A 
mouse died after two hours' exposure to an atmosphere containing 
only 0.06 per cent. ; a guinea pig after seven hours' exposure to an 
atmosphere containing 0.24 per cent. The poisonous effect seems 
to be due to the action of the sulphurous acid on the blood, which 
absorbs the gas and oxidizes it to sulphuric acid. 

Hirt claims, however, that air containing even as much as 4 per 
cent, of the gas has no permanent ill effect on the health of human 
beings, but one-tenth of that amount occasions difficulty of breath- 
ing (Wagner). 



BLEACHING. 275 



CHAPTER IV. 

BLEACHING. 

None of the commercial processes for separating cellulose which 
have been thus far considered yield this material in a state of com- 
plete purity. It is always associated with a portion of the lignin 
or incrusting matter originally present in the raw fibre, and various 
coloring-matters may also be present. The lignin is more or less 
modified by the treatment to which the fibre has been subjected, and 
the coloring-matters may be either those which have survived this 
treatment, or those which have been developed as a consequence 
of it. The coloring-matter properly so-called usually forms only 
a small proportion of the foreign material, so that most of the 
work of the bleaching agent is spent in the destruction of lignin 
and those derivatives of lignin which were formed and left upon 
the fibre in the processes of reduction. The process of bleaching, 
by which these impurities which cover up the natural white of the 
pure cellulose are removed, is -essentially a process of oxidation, 
and depends for its success upon the fact that the substances asso- 
ciated with the cellulose are more easily oxidized and split up into 
soluble products by an oxidizing agent than the comparatively 
stable cellulose which forms the basis of the impure fibre. The 
destruction of these impurities may be brought about through the 
action of almost any of the well-known oxidizing agents, and many 
of them have been applied for this purpose with more or less suc- 
cess. Practically, however, all bleaching is effected by the use 
of chlorine, or compounds of chlorine, which, in the presence of 
moisture, set up reactions by which oxygen is liberated. Of these 
compounds the hypochlorite of calcium, " chloride of lime," or 
ordinary bleaching-powder, is by far the most important. 

The commonly accepted and probably the true theory of hypo- 
chlorite bleaching is, therefore, that the destruction of the coloring- 
matter is due primarily, not to the action of the chlorine, but to 
that of oxygen which is set free in the decomposition of water 
brought about by the chlorine, which unites with the hydrogen of 



276 THE CHEMISTRY OF PAPER-MAKING. 

the water to form hydrochloric acid. Bleaching, therefore, becomes 
a form of burning or wet combustion, in which the coloring-matters 
are oxidized by the liberated oxygen, the final products of the 
oxidation being carbonic acid and water ; while the cellulose, being 
freed from the foreign matter with which it was at first associated, 
appears in its natural, uncolored condition. Dry chlorine has no 
bleaching action whatever, as may be shown by placing a piece of 
litmus paper, or a piece of cloth dyed a delicate tint, in a jar filled, 
with the dry gas. If care has been taken to exclude all moisture* 
there will be no change in the color after several hours' exposure 
to the gas ; but upon the addition of water the color is instantly 
discharged. Chlorine does not, as a rule, destroy mineral colors* 
or the blacks and grays produced by lampblack or deposited 
carbon. 

Chlorine was first applied to bleaching by Berthollet in 1785, 
who employed a solution of the gas in water. Tennant in 1798 
patented a liquid bleach, which was a solution of calcium or sodium 
hypochlorite, prepared by passing the gas into milk of lime or a 
solution of caustic soda. This bleaching agent was necessarily 
difficult to transport and keep, and in 1799 he introduced a 
great improvement by preparing a solid bleaching agent by pass- 
ing the chlorine gas over slaked lime, which absorbed it with 
formation of hypochlorite of calcium. 

Despite the obvious advantages offered by the use of bleaching- 
powder, its introduction was very slow, and there are doubtless 
many paper-makers in this country whose recollections go back 
to the time of gas bleaching. In working this method chlorine 
gas was generated at the mill by the action of sulphuric acid upon 
a mixture of peroxide of manganese and common salt in a stone or 
stoneware retort fitted with earthenware pipes, through which the 
gas was conducted to the moist pulp stored in the drainer. The 
inconvenience and disadvantages of this early method were so 
great that it has now been wholly discarded in favor of the more 
manageable bleaching-powder. 

The method of preparation of ordinary bleaching-powder has 
been described in Part I., and the various methods for testing its 
value will be found in the chapter on Chemical Analysis. As 
ordinarily manufactured it is white powder having a somewhat 
pungent but not disagreeable odor of chlorine. If very strong, it 
usually contains some lumps. When exposed to the air it rapidly 



BLEACHING. 277 

absorbs moisture, and is converted into a sticky mass, or even into 
a gray mud. The exact chemical composition of bleaching-powder 
has been a matter of some controversy, but the formula CaOCl 2 
proposed by Lunge is now being generally accepted. The com- 
mercial value of the material depends upon the amount of chlo- 
rine present as hypochlorite, this chlorine being commonly called 
" available chlorine." In the freshly manufactured article the per- 
centage of available chlorine may be as high as 41 ; but as found 
in our markets, and owing to the deterioration which always takes 
place in storage, the percentage of available chlorine is rarely 
above 37, and anything over 36 is usually accepted as satisfactory. 
The strength of bleaching-powder is estimated in France in 
degrees, which represent the number of litres of chlorine gas at 
0° C. and 760 mm. pressure which can be liberated from one kilo 
of the sample. The relation which these degrees bear to the per- 
centage of effective chlorine is shown below: — 



French 
degrees. 

65 


Per cent, effective 
chlorine. 

20.65 


French 
degrees. 

100 


Per cent, effective 
chlorine. 

31.80 


70 


22.24 


105 


33.36 


75 


23.83 


110 


34.95 


80 


25.42 


115 


36.54 


85 


27.01 


120 


38.13 


90 


28.60 


125 


39.72 


95 


30.21 


130 


41.34 



One litre of chlorine weighs 3.18 grammes, and the percentage 
may therefore be calculated by multiplying the French degrees by 
0.318. 

The deterioration of the strength of bleaching-powder is very 
rapid when the powder has been wet, as sometimes occurs on ship- 
board, and we have tested samples containing less than 28 per cent, 
of available chlorine. In rare cases the powder is liable to sudden 
decomposition, in which oxygen is liberated, and instances are on 
record in which casks of bleach have exploded from this cause. 

The best series of experiments which have come under our 
notice having for their object the determination of the rate at 
which bleaching-powder deteriorates in storage are those of Pat- 
tinson, which extended over a year, and were concluded in 1886. 
He took 3 casks of the usual size, each containing about 6 cwt. of 
bleaching-powder; 12 bottles of each kind of powder were filled at 



278 



THE CHEMISTRY OF PAPER-MAKING. 



the same time, the casks sealed, and both casks and bottles stored 
in a cellar. A maximum and minimum thermometer was placed 
near them, and a careful record of the temperature made for each 
working day of the year. The record shows the temperature to 
have been uniform and comparatively low during the entire year, 
the highest being 62° F., and the lowest 38° F. One bottle from 
each of the 3 sets of 12 was opened and tested each month, and a. 
sample was also withdrawn and tested from each of the 3 casks. 
The results of the experiments show a gradual and regular loss 
of available chlorine during the time over which the tests were 
made. The average loss in the cask samples was about a third of 
1 per cent, greater than in the bottle samples, as the casks were 
necessarily not air-tight. A complete analysis of each of the cask 
samples was made at the beginning and also at the end of the 
experiment. These analyses are given in the table below : — 

Composition of Bleaching-Powder. 





January 29, 


1885. 


January 5, 1886. 




A 


B 


C 


A 


B 


C 




37.00 


38.30 


36.00 


33.80 


35.10 


32.90 


Chlorine as chloride .... 


0.35 


0.59 


0.32 


2.44 


2.42 


1.97 


Chlorine as chlorate .... 


0.25 


0.08 


0.26 


0.00 


0.00 


0.00 




44.49 
0.40 


43.34 
0.34 


44.66 
0.43 


43.57 
0.31 


42.64 
0.36 


43.65 




0.38 




0.40 


0.30 


0.50 


0.50 


0.40 


0.50 




0.18 


0.30 


0.48 


0.80 


1.48 


1.34 


Alumina, peroxide iron, oxide "> 
manganese / 


0.48 


0.45 


0.35 


0.40 


0.40 


0.37 




16.45 


16.33 


17.00 


18.18 


17.20 


18.89 




100.00 


100.00 
38.97 


100.00 
36.58 


100.00 
36.24 


100.00 


100.00 




37.60 


37.52 


34.87 



The small quantity of chlorine found as chlorate at the begin- 
ning of the experiments ceased to exist in this combination at the 
end, and from tests made it was found that all the chlorate had 
disappeared in May, or about four months after the casks were 
filled. The amount of chlorine existing as chloride had slightly 
increased. It is not often the bleaching-powder can be stored where 
so low a temperature as 60° F. can be maintained for any length 
of time, especially in the summer months, when, as previous experi- 
ments have indicated, the greatest loss of available chlorine takes 
place. 



BLEACHING. 279 

Bleaching-powder should be stored in as dry a place as possible, 
or, better, in one that is both dry and cool ; and if any casks are 
damaged, they should be the first ones selected for use, as deterio- 
ration is likely to proceed more rapidly in them than in sound casks. 

The rate at which the powder deteriorates is largely influenced 
by the quality of the cask in which it is packed. The soft woods 
are considerably affected by the action of the powder, and shrink 
badly when exposed to the sun. In any subsequent exposure to 
rain, therefore, the water readily finds its way into the cask. Ash 
and other hard woods may be properly used for staves ; but the 
best casks are built of oak staves one inch in thickness. The pores 
of oak are very close, and almost impervious to the air, and if, as was 
formerly the usual case, the staves had previously been used for raw 
sugar or molasses casks, they are still better fitted to preserve the 
bleach. Many makes of bleach arrive in casks with staves |-inch 
or |-inch in thickness, but thicker staves are to be recommended. 

For the preparation of the hypochlorite solution, one-half the 
contents of the cask are dumped into about 1000 gallons of water in 
an agitator tank which is built of iron and well painted with red lead. 
Agitation of the mixture is continued until all lumps are broken 
up. The agitator is then stopped, and the greater portion of the mud 
allowed to settle, after which the cloudy liquid standing above is 
drawn out into shallow tanks to complete the deposition of sedi- 
ment. The mud remaining in the agitator is again treated with 
a fresh quantity of water, and the weak liquor thus obtained is 
drawn off into another tank, and used in the first treatment of the 
next lot of bleaching-powder. The mud should be tested from 
time to time for available chlorine, as unless the washing is thor- 
oughly performed a considerable loss may occur. 

We are indebted to Hoffmann's Handbook for the following 
analysis of the mud from chloride of lime solutions. On account 
of the variation in the quality of bleaching-powder, however, this 
analysis cannot do more than indicate in a general way the char- 
acter of the mud. 

Analysis of Dry Mud from Bleaching-Powder Solution. 

Hydrate of lime (CaH 2 2 ) 59.28 

Carbonate of lime 27.81 

Chlorite of calcium . 5.98 

Oxide of iron and alumina 1.00 

Water . . . . 5.42 



280 THE CHEMISTRY OF PAPER-MAKING. 

Only the clear solution prepared as above should be used for 
bleaching, not only because it acts more quickly than a cloudy one 
which contains considerable free lime, but also in order to avoid dirt. 
Many of the black specks noticed in paper are due to dirt in the 
bleach. When from this source, they generally consist of iron 
oxide, and traces of copper may be found in them. The best 
strength of liquor for storage and for economy, and thorough 
washing of the mud, is about 5° Be\ The hydrometer gives, of 
course, only a rough approximation to the strength of the bleach, 
since both the chlorate and chloride of calcium affect the instru- 
ment quite as much as the hypochlorite, but as a rough rule it 
may be stated that 1° Be. averages about 0.47 per cent, available 
chlorine in the solution. 

The bleaching of paper-stock is performed either in chests or 
engines. Rags and jute are bleached in engines, wood and simi- 
lar fibres more commonly in chests. The difficulty of securing 
thorough agitation and evenness of color in chests is an objection, 
and their use requires a larger plant to do the same amount of 
work. 

The amount of bleaching-powder actually consumed in bringing 
stock to color depends mainly, of course, upon the thoroughness 
with which the non-cellulose has been removed by the previous 
treatment. On this account the results obtained by different mills 
in bleaching the same fibre show considerable variation. It is to 
be noted, moreover, that the mills base their figures upon the 
weight of bleach in the cask, and that considerable losses may 
occur in mixing the bleach and washing the mud. The follow- 
ing may be taken as the usual quantities of bleaching-powder 
required per 100 lbs. of the different fibres. 

Lbs. 

Rags 2-5 

Straw . 7-10 

Esparto 10-15 

Soda Poplar 12-15 

Soda Spruce 18-25 

Sulphite Poplar 14-20 

Sulphite Spruce 15-25 

Jute 10-20 

The full proportion of bleach in the form of a 5° Be. solution 
is usually added after the stock has been well beaten up. It is 



BLEACHING. 281 

best to have the stuff as thick as possible without interfering with 
thorough agitation. The general tendency is to add considerably 
more bleach than the stock requires. This has the effect of 
hastening the operation, but the loss in the drainage water may 
be great. 

We have frequently tested the liquor in the chest, in order to 
determine the proportion of chlorine present after the pulp had 
come to color, and have found in many cases that it amounted to 
one-quarter or more of that originally introduced. 

The bleaching of rags is a comparatively easy operation, since 
the preliminary treatment has removed nearly all the material 
other than cellulose. The half-stuff is always bleached in the 
engine, and requires from 2 to 5 per cent, of bleaching-powder. 
A small amount of acid is often added when color is nearly 
reached, and in the best practice the stock is dumped into drainers, 
and there gradually brought to full color by the last portions of 
bleach remaining in the stock. 

Wood fibre is bleached either in engines or chests, the latter 
practice being more common. The pulp is sometimes dumped 
into the drainer after a treatment of about two hours in the engine 
with strong bleach solution. Bleaching in the chest requires from 
six to sixteen hours, according to the character of the pulp, and, 
on account of the difficulty of securing thorough agitation, is less 
likely to give an even color, especially when the stock during 
bleaching is heated by steam. 

After the pulp has come to color the action of the bleach should 
be arrested as soon as possible, either by washing or the use of 
an antichlor, as otherwise the cellulose itself is likely to have its 
strength and quality impaired through the continued oxidizing 
action of the hydrochlorite. 

The operation of bleaching is frequently accelerated by heating 
the mixture of pulp and bleach liquor by means of a steam pipe 
passing to the bottom of the chest or engine. Considerable care 
is necessary in order to avoid over-heating ; and if the temperature 
much exceeds 100° F. the chlorine is likely to attack the cellulose, 
forming organic chlorides, which remain with the fibre and cause 
the color to go back. This chlorination of the fibre is likely to 
occur when a considerable proportion of lignin is present, and it 
is claimed that where, as in the case of soda poplar pulp, the 
lignin has been entirely removed, a considerably higher tempera- 



282 TEE CHEMISTBY OF PAPER-MAKING. 

ture may be maintained without injury to the stock. Although 
there is an undoubted saving of time by hot bleaching, the experi- 
ments of Cross and Bevan indicate that the consumption of bleach 
is increased about 20 per cent., in order to secure the same result 
as regards color. 

The admission of steam into the bottom of a deep chest intro- 
duces a danger which it is difficult to avoid. If the movement of 
the pulp is slow, or if the stuff is very thick, the mixture in the 
lower portion of the chest may, on account of the imperfect cir- 
culation, easily become so hot as to injure the pulp, while the tem- 
perature at the surface may be much below this point. Such 
local over-heating is a common cause of uneven color in the fibre 
bleached in chests. 

In order to free the cellulose from traces of chemicals which, 
are likely to affect its permanence, all pulp should be washed after 
bleaching, even though the active chlorine has been " killed " by 
the use of an antichlor. Small traces of free acid or of chlorides 
cause paper to deteriorate rapidly through the formation of hydro- 
cellulose in the first instance, and on account of changes set up 
by reactions which are less perfectly understood in the second. 
Chloride of alumina, even in small amounts, is known to have a 
very destructive effect upon cellulose, and would be formed on 
the addition of alum to pulp containing chloride. Traces of bleach 
seriously impair the strength of pulp by converting it into the 
brittle oxycellulose. This action is well shown if a piece of cotton 
is dipped into a dilute solution of bleach, and then squeezed nearly 
dry and exposed to the air, when it will be found to undergo a 
gradual disintegration. 

The presence of traces of bleach in the stock may be readily 
detected by the use of iodide of starch paper or solution. The 
latter is made by boiling up as much starch as would go on a 
ten-cent piece with five or six ounces of water, and adding a few 
crystals of iodide of potash. The paper is prepared by dipping 
pieces of filter paper into the mixture. The paper is somewhat 
more sensitive if used at once, but it may be dried and preserved 
for future use. If a drop of liquor containing bleach is brought 
in contact with either the solution or the paper, iodine is liberated, 
and forms immediately with the starch a deep blue compound. 
Two precautions should be observed in making this test ; if the 
bleach liquor is very strong, there may be sufficient chlorine pres- 



BLEACHING. 283 

ent to destroy the blue, while, on the other hand, the chlorine 
may sometimes be so nearly exhausted that no test for it can be 
obtained from the liquor, although the blue color appears when a 
drop of the starch reagent is allowed to fall upon the pulp itself 
from which the liquor has previously been squeezed. 

A yellowish discoloration is sometimes noticed on the top and 
edges of wet bleached pulp which has been kept for some time. 
This is due generally, if not always, to imperfect washing, by 
which all the calcium chloride is not removed after bleaching. 
The evaporation going on at the exposed portions, aided by the 
capillary action of the pulp which continually brings more water 
from the interior of the mass, gradually concentrates the solution 
of chloride which may at first be extremely dilute, until it is 
strong enough to act upon the fibre and form these colored 
decomposition products. The water extract from such yellow 
portions is found by us to be dark colored and bitter. It contains 
calcium chloride in considerable amount. The residue left after 
evaporating the extract yields, on treatment with alcohol, a light 
brown solution which gives a copious yellow precipitate with a 
neutral alcoholic solution of lead acetate ; the substances present 
in the extract seem to be nearly allied to caramelane. 

The time required and difficulty experienced in removing the 
last traces of bleach from the pulp by washing has led to the use 
of various chemicals for the purpose of neutralizing any hypo- 
chlorite left in the stock. Such chemicals are called, from their 
office in this connection, Antichlors. 

Sodium thiosulphate, Na 2 S 2 3 , 5 H 2 0, commonly called "hypo- 
sulphite of soda," is the antichlor most used. It is dissolved in 
water, and added in small quantity to the engine after the pulp 
has come to color. When brought into contact with bleach liquor, 
the following reaction occurs : — 

2(Ca(C10) 2 ) + Na 2 S 2 3 + H 2 = 2 CaS0 4 + 2 HC1 + 2 NaCL 

in which the products are calcium sulphate, or Pearl Hardening, 
hydrochloric acid, and common salt. Every 409 parts of active 
bleaching-powder (35 per cent.) here requires 248 parts of the 
hyposulphite. This is the reaction as usually given and as it 
commonly occurs, but if the solutions employed are very dilute, 
the decomposition may take place in another direction, viz. : — 

Ca(C10) 2 -l- 4 Na 2 S 2 3 + H 2 = 2 Na 2 S 4 6 + 2 NaCl + 2 KaOH + CaO. 



284 THE CHEMISTRY OF PAPER-MAKING. 

The use of hyposulphite of soda is open to the objection that 
the products of either of the above reactions are nearly as preju- 
dicial in the paper as the traces of bleach which might remain 
after washing. If more than a small quantity of antichlor is used, 
the stock should afterwards be washed. Sodium sulphite, Na 2 S0 3 , 
which neutralizes the bleach after the manner shown, — 

Ca(C10) 2 + 2 Na 2 S0 3 = CaS0 4 + NaS0 4 + 2 NaCl, 

has been used abroad as a substitute for the hyposulphite, and is 
to be preferred, and not only because it is more efficient weight 
for weight, but because the products of its action are less likely 
to have an injurious effect upon the paper, in case they are not 
thoroughly washed out. 

Calcium sulphite, CaS0 3 , is used to a considerable extent in this 
country under the name of Hosford's Antichlor. It is found in 
the market in the form of a very fine, smooth powder, nearly white, 
and showing a granular structure under the microscope. On 
account of the slight solubility of the salt, the reaction, — 

Ca(C10) 2 + 2 CaS0 3 = CaCl 2 + 2 CaS0 4 , 

upon which its value depends, proceeds rather slowly. Any excess 
of this antichlor goes into the paper to make weight, and is quite 
unobjectionable, except possibly in the presence of very delicate 
colors. The chloride of calcium resulting from the reaction should, 
however, be removed by washing, since, when present even in 
traces, it hastens the deterioration of the paper. Kellner has 
advocated the addition of sulphite of lime to the stock, on the 
ground that it retards the aging and yellowing of papers which 
have been heavily sized with rosin, or which contain ground wood. 
The ordinary sulphite liquor used in the manufacture of wood 
pulp forms, as will be readily inferred from the last two paragraphs, 
a very efficient antichlor. As the sulphites are in solution, the 
action of the liquor is rapid, and its use in many cases tends to 
brighten the color, though this effect is not likely to be permanent. 
Any considerable excess of the liquor is to be avoided unless the 
pulp is to be afterwards washed, as otherwise there is danger that 
traces of free sulphuric acid may be formed in the paper through 
the oxidation of the bisulphite, and cause a rapid deterioration 
in the strength of the fibre, besides corroding the wire and rusting 
the dryers of the paper-machine. 



BLEACHING. 285 



The mixture of calcium thiosulphate and polysulphide, made by 
boiling together milk of lime and sulphur, has been proposed as a 
cheap and effective antichlor ; but since a considerable proportion 
of free sulphur is precipitated by the action of the bleach upon 
the mixture, its use is not to be recommended. The sulphur is 
left in the iibre in such a finely divided condition as to be slowly 
changed into sulphuric acid by ordinary atmospheric influences, 
and as a result there is a gradual conversion of the fibre into the 
brittle hydrocellulose. The free sulphur is also likely to cause 
rotting of the wire through formation of metallic sulphides. 

Lunge recommends the use of hydrogen peroxide as an antichlor. 
It removes the oxygen from the hypochlorite, and is at the same 
time decomposed into water and free oxygen. Its use offers none 
of the objections which can be urged against the other antichlors 
on account of the products which they leave in the paper, and 
the durability of the bleached stock is rendered more assured. 
The reaction is a noteworthy one, inasmuch as it furnishes an in- 
stance of one powerful oxidizing agent being reduced through the 
action of another oxidizing agent. 

In many cases, and especially in sulphite pulp, which before 
bleaching contains a considerable proportion of only slightly modi- 
fied incrusting matter, it is much easier to obtain a cream or 
slightly yellow tone in the bleached fibre than the pure white, 
which is desired. This color is largely due to the yellow tint 
of the insoluble chlorinated compounds formed by the action of 
bleach upon the ligno-cellulose, and on that account is an evidence 
of the presence in the pulp of compounds which considerably 
impair its quality, aside from the mere question of color. It is 
possible by the judicious use of blue, the color complementary to 
yellow, to mask this undesirable appearance of the pulp . and 
greatly improve its apparent color. This practice is not uncommon 
in case of pulp which is offered for sale, but the improvement in 
color is quite fictitious and serves only to disguise the true quality 
of the pulp. In extreme cases the sophistication is apparent to 
the eye, or may be detected at once by the bluish tint observed on 
looking through a sheet of the suspected pulp. If the quantity 
of blue used has been more carefully proportioned, its presence 
may nevertheless be usually detected by rolling the suspected 
sheet into a tube and looking through it, or by looking into a fold 
of the pulp as into a partly opened book. In each of these cases 



286 THE CHEMISTRY OF PAPER-MAKING. 

the blue is intensified by the multiple reflections of the light 
before reaching the eye. 

Even when a yellow tint is not apparent in the bleached fibre, 
it often contains an appreciable quantity of chlorinated cellulose. 
"We have found in bleached sulphite pulp of good color between 
5 and 6 per cent, of this material. The same pulp, after warming 
to 100° F. for eight hours with weak bleach solution, contained 
10 per cent, of the chlorinated cellulose, an increase of about 
5 per cent., while a portion treated with the same bleach solution 
in the cold for the same time showed an increase of the chlorinated 
cellulose of only 2 per cent. 

To show still further the action of warm bleach solution, we 
treated a sample of pure cellulose with dilute bleach solution at 
a temperature of 140° F. for four hours. The sample, after 
thorough washing and drying, showed a loss of 6|- per cent., while 
the dried sample was found to contain 19 per cent, of chlorinated 
cellulose soluble in very weak soda. One-quarter of the cellulose, 
then, in this experiment had been changed, and nearly one-tenth 
(allowing for the increase of weight by the chlorine absorbed) 
actually burned up and dissipated. 

Many of the highly lignified bast fibres, like jute, manila, and 
hemp, are especially liable to chlorination, and fail to come to good 
color when subjected to the ordinary process of bleaching. These 
compounds of chlorine with the fibre substance range in color 
from bright yellow to orange, and develop a magnificent magenta 
when treated with a solution of bisulphite of soda. They are 
readily soluble in alkalies, and may be removed from the fibre by 
treatment with a 1 to 2 per cent, solution of soda-ash. 

Besides the chlorination mentioned, which is a danger that care 
will usually avoid, there is always in bleaching a slight oxidation 
of the external layers of cellulose which is sufficient to affect the 
chemical relations of the fibre itself to certain coloring-matters. 
This change of relationship is mainly due, in the case of paper 
pulp, to the formation of a superficial layer of oxycellulose, which 
has a marked affinity for the basic coloring-matters and the power 
of withdrawing them from their solutions. If the oxidation ex- 
tends into the substance of the fibre it occasions a considerable 
loss of strength. 



BLEACHING. 287 

The following analysis, made by ourselves, may be taken as 
indicative of the composition of well-bleached fibre : — 

Analysis of Filter Paper. 

{Schleicher and SchuWs Wo. 597.) 

Per cent. 

Moisture, loss at 100° C 5.26 

Mineral matter, ash 0.37 

Hydrocellulose, etc. (soluble in alcohol) . . 0.73 

Cellulose 93.69 

Lignin, etc. . none 

100.05 

. We have obtained the following analytical and experimental 
figures from two samples of unbleached spruce pulp made by the 
sulphite process. A was a sample of what may be called normal 
pulp, whereas it had been found impossible in practice to bleach 
B to anything like good color. The latter sample contained, as 
will be noted, 0.34 per cent, of waxy material removable by carbon 
disulphide, and our examination showed that to this material the 
difficulty which had been experienced was mainly due. The 
material contained sulphur in combination, and was most probably 
formed during boiling by the action of the liquor upon some of 
the constituents of the wood. The presence in the liquor of the 
higher and easily decomposed sulphur acids is known to com- 
plicate the boiling process, and it is not impossible that this waxy 
material was the result of abnormal reactions thus occasioned. 
The objectionable substance was in any case so modified by the 
bleaching as to be removable by washing with very weak acid and 
alkali, and the color of the sample thus washed was beyond 
criticism. 

A. B. 

Moisture 7.00 7.89 

Organic matter removed by bleaching 2.35 3.39 

Waxy material removed by carbon disulphide after 

bleaching and drying — 0.34 

Hydrocellulose, gums, etc., remaining in bleached pulp, 

soluble in dilute caustic potash (1 per cent.) . . . 2.76 2.17 
Mineral matter removed by weak acid (1 per cent. HC1) 0.60 1.10 
Mineral matter remaining in bleached pulp after treat- 
ment with potash and acid 0.22 0.27 

Cellulose 87.12 84.83 

100.05 99.99 



288 



THE CHEMISTRY OF PAPER-MAKING. 



A B 

Apparent loss in bleaching 1.40 2.31 

Mineral matter added by bleaching process .... 0.95 1.08 

Actual organic matter lost in bleaching 2.35 3.39 

Chlorination of fibre in bleaching none none 

Bleaching-powder (35 per cent, available chlorine) 

consumed 16.90 18.80 

Time of bleaching experiment, 4|- hours at about 50° C. 

Color obtained good bad 

(greenish) 

Pulp, after bleaching and treatment with potash and 
acid, contained : — 

Cellulose . . 99.78 99.73 

Mineral matter (ash) 0.22 0.27 

100.00 100.00 

Ash of pulp as received 0.82 1.37 

Ash of bleached pulp before treatment with potash and 

acid (original moisture basis) 1.79 2.51 

Color of bleached pulp after purification with potash 

and acid good good 

O'Neill gives the following interesting results of experiments 
made to determine the tensile strength of cotton threads before 
and after bleaching, by measuring the strain required to break the 
thread. The calico experimented on was of good quality, and had 
sixteen to eighteen threads to the £-inch; the length taken for 
testing varied from 0.25 inch to 3.1 inch. 





Average weight required to hreak 
a single thread. 




Before bleaching. 


After bleaching. 


No. 1 " warp " 

No. 2 " " " 

No. 3 " " " 


1714 grains 
3140 " 
3407 " 
3512 " 


2785 grains 
2920 " 
3708 " 
4025 " 



It is seen, says the author quoted, that in two cases out of 
three, the warp threads are stronger after bleaching than before, 



BLEACHING. 289 



and in one case a little weaker. All that can be safely concluded 
from numerous trials made is, that the tensile strength of the 
cotton yarn is not injured by a careful but complete bleaching, 
and probably it may be strengthened by the wetting and pressure 
causing a more complete and effective binding of the separate 
cotton hairs or filaments, the twisting together of which makes 
the yarn. 

There is a generally received opinion among the manufacturers 
of soda pulp that it is impossible to bleach their stock to good 
color, if more than a slight trace of alkali remains in the fibre. 
The difficulty is usually attributed to the presence of the alkali 
itself, but, as excellent results in bleaching may be obtained by 
the use of an alkaline solution of sodium hypochlorite, this is 
evidently an error. The trouble is really due to the presence of 
the organic matter in the small amount of black liquor still 
remaining in the pulp, and with which the alkali is associated. 

We have made a large number of experiments in elucidation of 
this point, and find that a small proportion of such soluble organic 
matter remains in even very well washed brown pulp as taken 
from the mill. Forty grammes dry of such well washed poplar 
pulp required for its complete extraction 3800 cc. of distilled water 
before the percolate failed to give a test for organic matter, and the 
total amount of chlorine consumed by the organic matter extracted 
amounted to 0.053836 grammes. When the washing has been well 
conducted at the mill, we find a remarkably close agreement in 
the figures which represent the amount of organic matter still 
remaining in the pulp of different mills. The amount of chlorine 
consumed by the organic matter extracted per 100 grammes dry 
pulp closely approximating 0.135 grammes. 

In order to determine the effect of this small quantity of soluble 
organic matter upon the bleaching process, we have in a number 
of cases percolated several successive lots of pulp with the same 
water, after which another portion of pulp was mixed up with the 
percolate, and bleached in the usual way. For comparison, a 
quantity of pulp similar to the last was beaten up with distilled 
water and similarly bleached. We give the results of one experi- 
ment. Four lots of brown poplar pulp, amounting in all to 266 
grammes dry, were successively percolated with the same water. 
Two fresh lots of pulp were then taken, each containing 88.6 
grammes of dry pulp. Lot A was beaten up with water, while lot B 



290 THE CHEMISTRY OF PAPER-MAKING. 

was beaten up with the percolate previously obtained. A bleached 
readily to good color in two and one-half hours, with a total 
chlorine consumption of 1.5954 grammes. B, at that time, was 
far from being bleached, and at the end of five hours B was still 
inferior to A in color, although fairly well bleached. The chlorine 
consumed by B amounted to 2.1493 grammes. That is, the organic 
matter extracted from 266 grammes of dry pulp was sufficient so 
to retard the bleaching process that more than double the time was 
required, while there was an increase in the chlorine consumption 
of 28.07 per cent. 

Where unfiltered water, or water highly colored by organic 
matter in solution, is used in bleaching, an appreciable quantity 
of bleaching-powder is required to bleach the water, and it will 
sometimes, especially in case of water colored by peat, be almost 
impossible to make the water entirely clear and colorless. This 
organic matter has, moreover, the same effect in retarding the 
bleaching of the pulp to color as that in brown liquor. We have 
made a number of experiments to determine the quantity of 
bleach consumed by different waters, and give a few of our results 
in the chapter on "Water. 

Cloudman has patented an apparatus especially adapted to the 
better bleaching and washing of soda pulp, which is thoroughly 
sound in principle, and which has proved itself very economical 
and efficient in practice. It is shown in Fig. 64, in which are 
sub-figures 1 and 2. Fig. 1 shows the apparatus in plan, and Fig. 2 
is a vertical longitudinal section of a modified arrangement of two 
chests in line with one another, and with the conveyor for the 
material to be bleached and the passage through which the pulp 
passes from the top of one chest into the bottom of the next chest 
shown in the plane of section. 

The apparatus consists of a series of chests fitted with agitators, 
washing-drums, and conveyors /. The bleach liquor is sent 
through the series in one direction, while the pulp is carried 
through in the opposite direction. The strong liquor entering the 
chest marked a 4 acts at first upon the pulp which has been nearly 
brought to color by contact with the weaker liquor in the other 
chests, while the nearly exhausted liquor entering the first chest a, 
expends its remaining strength upon the brown pulp which first 
passes into this chest. 

Each chest is provided with an inlet passage 5, the pulp entering 



BLEACHING. 



291 



the chest near the bottom through this passage, and, together 
with the pulp, the bleaching agent which has previously passed 
through the other chests of the series, is introduced so that both 
enter together at the lower portion of the first chest a of the series. 




l ^^^^^^^^^^^ Z^ZZ^SZS2ZSM^^S^SZmi 



Fig. 64. Cloudman Apparatus for Washing and Bleaching. 

A continuous flow of pulp and bleach liquor is maintained, so that, 
at each moment, the lower portion entering tends to displace 
that which has already entered, thus causing the mixture to rise 
gradually upward from the bottom to the top of the chest. By 



292 THE CHEMISTBY OF PAPER-MAKING. 

means of the conveyor and washing-drum at the top of the chest 
the pulp and liquor are partially separated when they reach the 
top. 

The brown pulp enters at the bottom of the first chest a, through 
the inlet passage b. As it reaches the top of the chest it is raised 
by the conveyor /, and discharged into the top of the inlet pas- 
sage b, leading to the chest a 2 . It passes through this chest, and 
is similarly raised and discharged by the next conveyor in the 
inlet to the chest a 3 . From the top of this chest it is again raised 
by the third conveyor and discharged into the inlet to the chest a 4 . 
The bleached pulp is taken by the conveyor from the top of this 
chest and is discharged through the outlet h. Simultaneously 
with the above operations the strong bleach liquor has been 
passing through the chest in reverse order, entering through the 
inlet a 4 , and being finally discharged as waste through the outlet e, 
leading from the chest a, into which the brown pulp has entered. 
The passage of the bleached liquor through the series is effected 
by means of the washing-drums d, which partially separate the 
liquor from the pulp, and which discharge into the inlet opening 
of the chest next preceding the one from which the liquor came. 
In this way, as bleaching progresses, the pulp meets stronger 
and stronger bleach liquor ; while, as the proportion of available 
chlorine in the liquor decreases, the proportion of coloring-matter 
present in the pulp upon which the liquor is then acting increases. 
This is, of course, a reversal of the conditions obtaining in the 
usual methods of bleaching, where, as it becomes increasingly 
difficult to oxidize the last portion of coloring-matter, there is less 
and less available chlorine present for the purpose. 

Use of Acid. — The careful use of small quantities of hydro- 
chloric or sulphuric acid in bleaching quickens the process by 
liberating hypochlorous acid, which is much more energetic in its 
action than bleaching-powder itself. The acid is best added after 
the pulp has nearly come to color, and should in all cases be 
diluted with several times its volume of water, and should then 
be poured into the chest or engine in a slow stream. A 
small amount of acid is as effective as a larger quantity ; its 
action is more gradual, and there is less danger of chlorination 
of fibre and consequent loss of color. The first addition of acid 
neutralizes the lime present and decomposes the hj^pochlorite to 
form, if hydrochloric acid is used, chloride of calcium and free 



BLEACHING. 293 



hypochlorous acid. The hype-chlorous acid gives up its oxygen 
and is reduced to hydrochloric acid, which reacts with a fresh 
quantity of the hypochlorite as before, and the cycle of reactions 
continues until all of the hypochlorite has been decomposed. 
A small amount of hypochlorous acid is thus continuously liber- 
ated, but never enough to injure the fibre unless an excessive 
quantity of the stronger acid has been added. It is best to add 
the acid in several successive portions, and to stop, if any strong 
odor of hypochlorous acid persists. 

Lunge recommended, several years ago, the use of small quan- 
tities of acetic acid in bleaching, in preference to the mineral acids, 
as its action is safer, while the amount required is so small that 
no objection can be made on account of cost. The acid has only 
recently been brought to the attention of the trade in a commercial 
wa}r, but its use in the bleaching of paper stock is now growing 
rapidly. About one gallon of the commercial acid is added to a 
1000-pound engine with the bleach liquor. It is stated, although 
the grounds for the claims are hardly apparent, that when used in 
connection with acetic acid, the amount of bleach may be reduced 
one-third, with the production of a cleaner and whiter half stuff. 
The results obtained in bleaching jute in this manner are said to 
be especially good. 

Treating- Jute. — Jute and similar materials derive their chief 
value as paper stock from the fact that the short ultimate fibres are 
bound together in the plant into filaments of great length and 
strength. In order that the stock may lend itself to the mechanical 
operations involved in the formation of a sheet of paper, it is nec- 
essary that these filaments be separated and partially broken down, 
but the methods of treatment are so regulated as to stop consider- 
ably short of such complete removal of the incrusting matter as 
would determine the separation of the ultimate fibres. The 
bleaching of such stock is therefore rarely carried beyond a good 
cream. 

Jute butts, as received at the mill, usually contain from 12 to 
18 per cent, of moisture. They are first cut into three or four 
slabs or pieces, and violently " thrashed " for a few minutes to 
remove the coarser particles of adhering dirt. A further cutting 
and dusting follows, after which the stock is ready for boiling. 
The loss in weight caused by this preliminary treatment usually 
varies from 7 to 10 per cent. 



294 THE CHEMISTRY OF PAPER-MAKING. 

The stock is boiled in rotaries for about twelve hours with milk 
of lime sufficient to rather more than half fill the rotary. The 
proportion of lime varies from 200 to 300 lbs. per ton of stock. 
In some mills the pressure is never allowed to exceed 15 lbs., while 
in others it is raised to 20 or even 30 lbs. The stock, after dump- 
ing from the rotary, is commonly allowed to remain on the floor 
for twenty-four to thirty-six hours to " temper," or soften, and is 
then thoroughly washed in an engine to remove all dirt and lime. 

Bleaching, properly so-called, is done in the engine, the chloride 
of lime being generally added as powder in the proportion of from 
10 to 20 per cent., according to the color desired and the thorough- 
ness of the previous treatment. 4 or 5 per cent, of acid alum is 
sometimes added to hasten the action of the bleach, but in this 
case or if the stock is heated, there is much danger of chlorinating 
the fibre and forming yellow compounds, which defeat the object 
of the process. The stock, after running two or three hours in the 
engine, is often dumped into drainers, where the bleaching is 
allowed to continue slowly for about a week. 

Bleaching Ground Wood. — Many paper-makers have ex- 
pressed a desire for a process of bleaching ground wood, but the 
matter presents several difficulties which are not likely to be 
overcome. Ground wood contains, of course, all the constituents 
of the wood itself, except the small proportion which was soluble 
in water. There is, therefore, in all such pulp about 50 per cent, 
of incrusting matter to be destroyed by the hypochlorite solution 
before a white color can be obtained, and any process of true 
bleaching would entail a corresponding shrinkage in the weight 
of the fibre and an enormous consumption of bleach. The first 
effect of the bleach liquor is to lower the color of the pulp to 
red or brown, and this shade persists until nearly all the incrusting 
matter has been destroyed. 

Although bleaching-powder is practically the only agent used 
for bleaching paper stock, various other bleach liquors have been 
proposed from time to time, and in some cases these possess ad- 
vantages which would warrant their introduction, were it not for 
their greater cost. Among these liquors are : — 

Magnesia Bleach Liquor. — This is prepared by adding Epsom 
salts to a solution of ordinary bleaching-powder, when calcium 
sulphate is precipitated and magnesium hypochlorite remains in 
solution. The clear liquor decanted from the precipitate is more 



BLEACHING. 295 



unstable, but also more energetic in its action than the liquor 
made directly from bleaching-powder. It is less caustic, and does 
not turn straw, hemp, flax, etc., brown, as is done by hypochlorite 
of calcium solution. This liquor is also known as Ramsay's or 
Crouvelle's bleaching-liquor. A solution of magnesium hypo- 
chlorite, prepared by the electrolysis of a 5 per cent, solution of 
magnesium chloride, has been used on the large scale by Hermite 
in his electric bleaching process, and the efficiency claimed for his 
bleaching-liquor is undoubtedly due more to its composition than 
to the method of its manufacture. 

Aluminum Bleach Liquor. — Sometimes called Wilson's bleach 
liquor, is prepared by treating a solution of bleaching-powder with 
one of alum. The reaction is similar to that which takes place in 
the preparation of the magnesium hypochlorite : that is, there is 
a precipitation of sulphate of lime, while the liquor consists of 
aluminum hypochlorite in solution. This liquor is exceedingly 
efficient, and the aluminum chloride which results from its decom- 
position is said to prevent the fungoid and other growths which 
sometimes appear as black specks upon bleached fibre. If this 
chloride is allowed to remain in the paper, however, it hastens 
the deterioration and yellowing of the sheet. Aluminum hypo- 
chlorite is formed, of course, when alum is added to the paper- 
engine, as is often the case in the ordinary process of bleaching ; 
and where the alum used is a neutral one, the increased rapidity 
of the bleaching action is due to the aluminum hypochlorite which 
has been formed. With an acid alum there may be, in addition, 
some liberation of free hypochlorous acid. 

Zinc Bleach Liquor. — By substituting zinc sulphate for the 
alum just mentioned, a solution of zinc hypochlorite is formed. 
This bleaches very rapidly, splitting up first into zinc oxide and 
hypochlorous acid. If the sulphate of zinc is added to the bleach 
liquor in the paper-engine, zinc oxide and sulphate of lime remain 
in the pulp. Zinc hypochlorite is sometimes called Varrentrapps' 
bleaching-salt. 

In certain English mills and bleacheries which are in close 
proximity to plants manufacturing bleaching-powder, there is 
often used a bleach solution which is prepared by passing chlorine 
directly into milk of lime. In this way an excellent liquor is 
prepared, which is even more efficient than that made up from 
bleaching-powder. It is not improbable that, with the development 



296 THE CHEMISTRY OF PAPER-MAKING. 

of the electrolytic processes for the decomposition of salt, this 
liquor may find a use in this country in plants which are con- 
veniently located to a source of chlorine. 

Among the bleach liquors which are at present rarely or never 
used may be mentioned Eau de Javelle and Eau de Labarraque. 
The former is made by passing chlorine into a solution of potassium 
carbonate, and the latter by similarly treating a solution of car- 
bonate of soda. In either case, the absorption of gas is continued 
until there is a slight effervescence, due to liberation of carbonic 
acid. If the caustic alkalies are substituted for the carbonates, 
similar but not identical liquors are prepared. 

It has already been pointed out that the hypochlorites vary 
with respect to the ease with which they are decomposed in the 
presence of coloring-matter, and the rapidity of the bleaching 
action therefore varies in the different cases. The hypochlorites 
of alumina, zinc, and magnesia, are considerably more rapid in their 
action than hypochlorite of lime. Hypochlorite of soda is slowest 
of all, but when very slightly acidulated the action is as rapid as' 
in case of any of the other hypochlorites named. 

Liquid Chlorine. — The advent of this material as a bleaching 
agent affords a curious example of the manner in which the 
development of a process sometimes follows lines which apparently 
bring one back at last to the point of starting, although in reality 
the new point .reached is on a higher plane. The early methods 
of gas bleaching were displaced by the simpler and more manage- 
able processes involving the use of hypochlorites, and it now seems 
not improbable that the economies and improvements recently 
introduced in the methods of manufacture and transport of chlorine 
in its elementary form may re-establish gas bleaching. 

The gas prepared from common salt, either by the well-known 
chemical methods or by the later ones which involve the use of 
electricity, is first dried and then brought to the liquid state by 
cooling and compression. The liquefied chlorine has a yellow 
color which is almost orange, and its specific gravity is 1.6602 at 
— 80° C. ; at 0° C. it is 1.4689 ; at 19° C, 1.4156 ; at 40° C, 1.3490 ; 
and at 77° C, 1.216. The coefficient of expansion is .00203 
between 15° C. and 20° C, and what is called the critical tempera- 
ture of the gas is 146° C, i.e., at any temperature higher than the 
one given, it is impossible by any increase of pressure to condense 
the gas into the liquid. 



BLEACHING. 



297 



The liquefaction is usually effected in 
stout wrought-iron drums, one form of 
which is shown in Fig. 65. This drum 
is provided with two valves ; and when 
a quantity of gaseous chlorine is desired, 
the drum is set up vertically, and the 
protecting-cap A is unscrewed. The plug 
B, or B', of one of the valves, is then 
removed, and replaced by a screw- 
coupling C. To this coupling is best 
connected a lead pipe for conveying the 
gas to the point of use. It is necessary 
to open the valve very slowly, as other- 
wise a sudden rush of gas may burst the 
convey ing-pipes. The conversion of the 
liquefied chlorine to the gaseous form 
is attended by so great an absorption of 
heat that the outside of the drum becomes 
heavily coated with frost, in which case, 
if a considerable amount of gas must be 
drawn off, it becomes necessary to raise 
the temperature of the drum, either by 
placing it in moderately warm water, or 
by wrapping it in hot cloths. The gas 
may be used for bleaching in the drainer, 
or it may be absorbed in water or in 
milk of lime. The latter method gives 
a liquor which is considerably more rapid 
and efficient in its action than any liquor 
made from bleaching-powder. Those who 
are interested in this new phase of bleach- 
ing will find an interesting and exhaus- 
tive paper on the subject by R. Kneitsch, 
in the " Annalen der Chemie," No. 259, 
page 100. He gives in the following table 
the pressure which the gas exerts on the 
inner surface of the cast-iron drums in 
which it is shipped. It will be noted that 
pressures are only for the ordinary temper- 
atures which lie between 0° and 40° C. 






298 THE CHEMISTRY OF PAPEB-MAKING. 



Temperature 
in°C. 


Pressure in 
Atmospheres. 


Temperature 
in °C. 


Pressure in 
Atmospheres. 





3.660 


+ 21.67 


6.960 


+ 9.62 


4.885 


+ 29.70 


8.652 


+ 13.12 


5.433 


+ 33.16 


9.470 


+ 20.85 


6.791 


+ 38.72 


10.889 



Use of Oxygen. — The brothers Brin, who have successfully 
attacked the problem of producing oxygen on a commercial scale, 
have made a large number of experiments with a view to the use 
of the gas as an auxiliary agent in bleaching with chloride of 
lime. It does not appear that the high hopes at first entertained 
for the process have been realized, although under favorable con- 
ditions, and where the stock to be bleached was thoroughly cooked, 
some saving of bleaching-powder was shown. Contrary to what 
was claimed at the time by the advocates of oxygen, no improve- 
ment was noticed in either the feel, appearance, or felting qualities 
of the resulting bleached stock. Since these first experiments 
were made, the price of oxygen has been materially lowered, until 
to-day it can be made for 0.05 cent per cubic foot under favorable 
circumstances. It is now claimed by those who control this 
process that in bleaching esparto, with ordinary bleach liquor plus 
oxygen, the quantity of bleach required can be reduced in the 
proportion of 2 to 1.25, so that, in a case where a ton of stock 
requires ordinarily 224 lbs. of 35 per cent, bleach, the use of 200 
cubic feet of oxygen saves no less than 84 lbs. 

Mr. Thorne, an expert in the use of oxygen for bleaching, claims 
that results can be obtained with oxygen which cannot be secured 
through the use of compressed air, and explains this rather curious 
phenomenon by the theory that the large amount of inert nitrogen 
which necessarily accompanies the oxygen when compressed air 
is used, carries away some oxygen and chlorine before the latter 
has time to act. 

So far as we are aware, no thoroughly satisfactory theory has 
been advanced to explain the action of oxygen when used in this 
way, for oxygen in the gaseous form has no especial bleaching 
power. 

Ozone Bleach. — The Fahrig electrostatic process for the pro- 
duction of ozone on a commercial scale has placed this powerful 
bleaching agent in a position which encourages its advocates to 
claim that it may yet successfully compete with the hypochlorites 



BLEACHING. 299 

in the bleaching of cellulose. It is already used with excellent 
effect for bleaching water ; 20 grains per 1000 gallons is sufficient, 
it is claimed, to give a good result, and it is already being used 
upon a considerable scale as a bleaching and oxidizing agent in 
various lines of industry, which are, however, foreign to our 
subject. It is usually employed in the form of a 1 per cent, solu- 
tion, although solutions containing 7 per cent, or 8 per cent, of 
ozone are sometimes made. 

Hydrogen peroxide is closely similar to ozone in its action, and 
is also attracting some attention as a possible substitute for hypo- 
chlorites. It is employed in the form of a weak solution, to which 
magnesia is sometimes added. 

Sulphurous Acid Bleach. — The bleaching action of sulphurous 
acid, as has been already pointed out elsewhere, differs essentially 
from that of the various oxidizing agents which have been con- 
sidered. In those methods of bleaching which involve oxidation, 
the coloring-matters are split up into much more simple oxidation 
products, which are themselves colorless. Sulphurous acid in only 
a few cases bleaches by the destruction of the coloring-matter, so 
that whatever value it possesses as a bleaching agent depends 
mainly upon its property of combining with the coloring-matter 
to form colorless compounds, from which the unchanged coloring- 
matters may be again liberated by the action of a stronger acid, 
or merely by continued exposure to atmospheric influences. Many 
of the brightly colored flowers, for example, may be bleached by 
exposure to the gas; but if they are then dipped in very weak 
sulphuric acid, the original color is restored. Wool and other 
animal fibres are generally bleached by means of sulphurous acid, 
and the color reappears when the acid combines with the alkali 
of the soap used in washing. 

In the best unbleached sulphite fibre the coloring-matters are 
merely masked, and more chloride of lime is required to bleach 
such fibre than is needed in the case of pulp which, through the 
use of higher temperatures, has had the incrusting matter more 
thoroughly removed, although its color is much poorer. The first 
effect of bleach ing-powder, as is well known, is to cause a marked 
lowering of color, as the first products of the oxidation are 
usually more highly colored than the original materials. If 
now an excess of bisulphite liquor is added to the pulp, the 
latter immediately becomes nearly or quite white, not on account 



300 THE CHEMISTRY OF PAPER-MAKING. 

of any true bleaching action, but because the sulphurous acid arrests 
the process of oxidation and conceals the coloring-matters by 
combining with them. The subsequent addition of an excess of 
bleaching-powder solution oxidizes the acid and restores the color 
as the first step in the resumption of the true bleaching process. 
It is therefore evident that any bisulphite liquor or sulphite of 
lime which remains in sulphite pulp, as a result of imperfect 
washing, consumes its equivalent of hypochlorite, if the pulp is 
subsequently bleached, and adds proportionately to the cost of 
bleaching. 



SIZING AND LOADING. 301 



CHAPTER V. 

SIZING AND LOADING. 

The infinite number of small spaces which exist within and 
between the fibres of a sheet of unsized paper, cause, by capillary 
action, a rapid spreading and absorption of any liquid with which 
the paper may come in contact. It is to this property that blot- 
ting paper owes its value, and there are a few other applications 
which require the use of an unsized or so-called " water-leaf " 
paper. Most of the uses to which paper is put, however, imply 
its contact with ink in one form or another, and it thus becomes 
necessary to so fill up the pores and coat the fibres with some 
material which shall offer sufficient resistance to the passage of 
fluid to prevent the spreading of the ink. This object is accom- 
plished by the various methods of sizing which we propose to 
consider in this chapter. 

The extent to which the sizing must be carried, and the nature 
of the sizing agents employed, depends upon the purpose for which 
the paper is to be used. Writing papers which are to come into 
contact with very fluid writing inks, require a much more perfect 
sizing than do printing papers for use with a thick and viscid 
printing ink. The division may be carried much farther, for 
while it is the object of some printing papers to retain the ink 
almost wholly upon the surface of the sheet, such papers as are 
used for other work in which quick absorption and rapid drying 
of the ink is necessary must have sufficient capillary power or 
" pull," as it is called, to accomplish these results. 

In the days of hand-made paper practically the only material 
used for sizing was gelatine, which was called animal sizing from 
its source, and tub sizing from its method of application, the size 
being formerly contained in a tub into which the paper was dipped 
by hand. 

With the advent of machine-made paper, and the application of 
the material to printing purposes, other methods of sizing came 
into use, until now the number of substances which have been more 



302 THE CHEMISTRY OF PAPER-MAKING. 

or less successfully adapted to the purpose is considerable. Prac- 
tically, however, all sizing is still done either with gelatine or 
rosin. The materials used for rosin sizing are applied to the 
beaten stuff either in an engine or chest, and this form of treat- 
ment is therefore known as engine sizing. 

Properties of Gelatine. — Pure gelatine is a colorless, odorless, 
almost transparent substance, having an insipid taste and being 
usually quite brittle. Its toughness, however, varies with its 
source. It softens and shrinks on heating, and gives off an un- 
pleasant nitrogenous odor on burning. It is insoluble in cold 
water, but swells and absorbs three or four times its weight of the 
liquid. In hot water it is freely soluble, and the strong solution 
upon cooling sets to a firm clear jelly. A firm jelly is hardly 
formed unless the solution contains about 7 per cent, of gelatine. 
With the best material even so little as 1 per cent, gives a gelati- 
nous mass on cooling. 

This power of gelatinizing is said to be destroyed by over-heat- 
ing the solution, or if the solution is frequently heated and cooled. 
The most conspicuous property of gelatine, and the one on which 
its value in the manufacture of leather depends, is found in its 
formation of an insoluble compound with tannic acid. Gelatine is 
also precipitated from its solution by alcohol, and is insoluble in 
ether and oils, but is dissolved by concentrated sulphuric acid in 
the cold. Alum does not precipitate it although it thickens the 
solution. If alkali is added to the mixture in sufficient quantity 
a precipitate is formed containing gelatine and a basic sulphate. 

The purest commercial form of gelatine is isinglass prepared 
from the swimming bladders of certain fish, notably the sturgeon. 
Glue is a comparatively crude form of the material, and is made 
by boiling down scraps of hide, horn, and hoof. Bones yield a 
similar but inferior product. The yield from raw-hide is about 
50 per cent. 

The production of glue in a commercial form involves several 
distinct operations, but the preparation of size is simpler partly 
because the raw material as purchased by the paper-maker has 
already undergone the treatment with lime, and partly because he 
only needs the glue solution, and therefore does not prepare a 
solid glue. The scraps received at the mill are soaked for several 
days in water, which is changed from time to time. Sometimes the 
washing is finished in drums or other form of washing apparatus 



SIZING AND LOADING. 303 

in which thorough agitation may be secured. Thorough washing 
is very important in order to remove traces of blood and any acid 
or lime remaining from the previous treatment to which the skins 
have been subjected. Arsenic, usually in the form of sulphide, is 
also sometimes present, it being brought into the skins by certain 
de-hairing processes. The washed pieces are next boiled with 
water, either in a tank, which may be lined with lead or copper, or 
else in a jacketed iron or copper vessel. Whatever the form of the 
vessel it is always fitted with a false bottom. 

The mixture is then heated up to a temperature varying from 
150° to 180° F., with the character of the material under treatment, 
and in about twelve hours extraction is completed.. Any grease 
which is present will have come to the top of the liquid, and must 
be carefully removed or otherwise kept out of the size. The solu- 
tion is cleared from suspended impurities and dirt either by set- 
tling or filtration. 

Alum is added to the size partly as a preservative, and partly 
because it is thought to render the gelatine somewhat more effi- 
cient as a sizing agent. The first effect of the addition of the 
alum is to thicken up the gelatine solution until it becomes very 
stiff, but curiously enough this is corrected by the addition of a 
further quantity of alum. Arsenite of soda is sometimes added 
as a preservative, but its use must be condemned on account of the 
poisonous nature of the material. 

In the process of animal sizing on the machine, which is now 
practically the only way in which this form of size is applied in 
this country, the web of paper is led through a trough filled with 
the size and to and from which a constant circulation of the liquid 
is maintained in order to prevent its becoming too cool for use. 
The drying of animal size in papers is a matter of nicety. If the 
best results are to be obtained, it is necessary that the drying be 
conducted slowly and at very moderate temperature. The com- 
moner way in the preparation of writing papers is to subject the 
sized paper after cutting, to a process of loft drying, in which the 
sheets are suspended on poles in a loft which is kept warm by 
steam pipes. By this slow drying, the glue is gradually brought in 
great part to the surface of the sheet, where its presence is most 
required. Cheaper grades of paper are sometimes dried on the 
machine, but in this case a large number of skeleton driers are sub- 
stituted for the steam drums which are ordinarily used as driers. 



304 THE CHEMISTRY OF PAPER-MAKING. 

Each of these skeleton driers has within it a fan for keeping up 
the circulation of the air, and the total number of such driers may 
be thirty-five or more. 

It is of the utmost importance that the size be entirely free from 
grease and acid ; the former is liable to make unsightly streaks and 
spots, while even traces of acids are likely to affect delicate colors 
and cause deterioration of the paper. Animal size is sometimes 
used in moderate amount directly in the engine, but its value at 
this point is doubtful, and in the absence of any substances which 
will precipitate the gelatine the greater portion of it is lost in the 
wash water. 

Engine Sizing. — We have already made reference on page 138 
to the more prominent properties of rosin. Its use in size depends 
upon its acid character by virtue of which it forms soaps with the 
various metallic oxides, and of course most readily with potash 
or soda. Its salts, which are those of the various acids which 
occur in rosin, are collectively called resinates. The resinate of 
soda, which at present most concerns us, is made by boiling rosin 
with a moderately strong solution of soda-ash or soda crystals, and 
is soluble in water. All resinates of metals other than those of 
the alkalis, are for the most part insoluble. The older theory of 
engine sizing is, that after the size has been diluted with water 
and mixed with the stuff it is precipitated as resinate of aluminum 
upon the addition of alum, and that this alum soap is the true 
sizing agent, which by coating over the fibres prevents the absorp- 
tion and spreading of liquid after the paper has been dried. The 
saponification of rosin in the preparation of size is rarely complete, 
and some free rosin is present in nearly all size. In some samples 
of white size as much as 25 per cent, of the rosin may be present 
as free rosin in a very fine state of subdivision. Commercial 
rosin contains also from 6 to 8 per cent, of unsaponifiable matter. 

According to the later theory of rosin sizing, for which we are 
in large measure indebted to the researches and conclusions of Dr. 
Wiirster, the precipitate produced by the addition of alum consists 
in the main of free rosin in a very fine state of division and mixed 
with a small proportion of resinate of aluminum. It is the view 
of Dr. Wiirster and many other chemists who have studied the 
matter, that the sizing effect is due solely to the free rosin, the 
resinate of alumina being quite inactive. Engine sizing, accord- 
ing to this view, consists merely in mixing very finely divided 



SIZING AND LOADING. 305 

rosin with the fibres, and then causing it to adhere and penetrate 
by the heat of the driers. We are ourselves disposed to adhere 
to the older view, for if free rosin alone is needed, equally good 
results should be obtained in sizing by the substitution of sulphuric 
acid for the alum usually employed. Our own results and those 
of Dr. Wurster indicate that such is not the case, but Lunge is 
said to have obtained good results by the use of sulphuric acid 
without alum. The true theory may perhaps lie between these 
two extremes, and define the office of the alumina as that of fixing 
the rosin upon the fibres. 

Preparation of Rosin Size. — Nearly every mill has its own 
receipt for preparing rosin soap for use in sizing, but except as to 
proportions the general method of procedure is about the same in 
all cases. The powdered or finely broken rosin is boiled in an 
alkaline solution in an iron kettle, preferably heated by a steam 
coil, although sometimes live steam is used. The darker colored 
rosin is believed to be the best, and as we think with good reason, 
since it has been distilled at a higher temperature, and therefore 
contains less pitchy matter than the lighter grades. At the time 
when practically all soda was made by the LeBlanc process, soda 
crystals were generally used, because of their greater purity and 
even composition. At present 58 per cent. Solvay soda-ash is 
almost universally employed, and it is undoubtedly the best 
material to use. The common practice in this country calls for 
quantities of soda-ash, which range from 20 to 40 per cent, on the 
weight of the rosin taken. 

Beadle, who has obtained the best results in sizing by the use of 
size containing 26 per cent, free rosin, recommends as the result 
of a large number of trials, the use of 1 lb. of soda-ash to every 
7.65 lbs. of rosin, or for 1300 lbs. of rosin, 170 lbs. of soda-ash 
and 200 gals, of water, the whole to be boiled for seven hours 
and then made to the volume of 225 gals, by addition of water. 
Size made by the above receipt contained : — 

Per cent. 

Combined rosin 40.59 

Free rosin 14.37 

Combined soda ......... 6.72 

Free soda 1.34 

During the boiling of size, considerable carbonic acid is evolved 
unless caustic soda is used, but the general experience has been 



306 THE CHEMISTRY OF PAPER-MAKING. 

that equally good results are not obtained with this material. The 
frothing due to liberation of carbonic acid when soda-ash is used, 
can generally be kept down if the sides of the kettle are not 
unduly heated, and for this reason where the steam jacket is used 
it should only cover the bottom of the kettle. In case the froth- 
ing becomes very violent, it may be checked by adding a little 
cold water through the sprinkler of a watering-pot, but even when 
the water is thus showered, it is apt to cause the formation of 
clots and make the size lumpy. 

The amount of water used in making size is a matter of impor- 
tance. With too much water the size sinks to the bottom with 
the dirt, whereas the aim of the size-maker should be to keep the 
solution of such density that the size will float, while the dirt 
sinks. 

New size is apt to make size spots, and it is, therefore, custom- 
ary to keep a supply ahead, and to draw for use upon that which 
is at least a week, and better, two or three weeks old. 

The following are our analyses of good average size as made by 
mills in this country : — 

A. B. 

Water 39.70 40.62 

Free rosin ...... 8.54 7.22 

Dry size 51.76 52.16 

Tallow is sometimes boiled up in small amounts with the rosin 
and is thought to improve the feel and finish of the sheet, but in 
the manner and small quantity in which it is used its value in 
these directions is doubtful. 

Action of Light on Rosin Size. — It has been known for a 
long time that both rosin and ground wood undergo some rather 
obscure changes on exposure to light and air, and that these 
changes were among the most important factors in causing the 
deterioration of paper by age. The subject has been investigated 
somewhat carefully by Herzberg. Five kinds of engine-sized 
paper, the size of which was proved normal by testing, were 
exposed to direct sunshine and air for a period of two months ; 
they were then tested, and exposed for another similar period. At 
the end of the second exposure, four samples out of the five were 
no longer fit to write upon. These were made of linen and cotton 
rags, some being with and some without ground wood pulp and 
straw. The fifth sample was made of ground wood and sulphite, 



SIZING AND LOADING. 307 

and gave an asli of 13.5 per cent. This was almost unaffected so 
far as the size was concerned, although the color was more altered 
than in case of any of the others. The exact nature of the change 
which takes place in rosin when exposed in this finely divided 
state to light, is not known, but Herzberg has proved that the 
change is due to light, rather than to the gases composing the 
atmosphere, since in other of his experiments, papers similarly 
exposed in tubes with oxygen and sulphuric acid were not 
affected so long as they were kept in diffused daylight. A piece 
of rosin kept for some time in direct sunlight loses its vitreous 
appearance and becomes covered with yellow powder. 

Use of Aluminate of Soda. — Certain advantages have been 
claimed for a method of preparing rosin size in which the saponi- 
fication of the rosin is effected by means of aluminate of soda, 
instead of carbonate of soda or caustic soda, as is usually the case. 
Aluminate of soda is a compound in which the alumina plays the 
part of a weak acid and enters into combination with the soda. 
From this compound alumina may be precipitated by the addition 
of acid or many salts. 

The rosin soap is prepared by boiling rosin in the usual manner, 
except for the substitution of aluminate of soda for the customary 
alkali. One part by weight of aluminate of soda is dissolved in 
four times its weight of water and added to two parts by weight 
of rosin. It is only necessary to have sufficient alkali present to 
thoroughly saponify and hold the rosin in solution, and the pro- 
portion just given may be greatly varied so long as this condition 
is met. The soap is added to the pulp in the beating engine in 
the usual manner, and is decomposed with precipitation of the 
rosin and alumina upon the addition of a soluble salt of magne- 
sium such as chloride or a sulphate. Chloride of calcium may 
also be used to advantage, or even ordinary alum, and the results 
in the latter case are said to be better with size prepared after the 
present method than are attainable through the use of a common 
rosin size. The strength of the solution used for the precipita- 
tion may be conveniently one part of the salt dissolved in twenty 
parts of water, but it is unnecessary to adhere closely to this for- 
mula. Where the magnesia salts are used the base is precipitated 
at the same time together with the rosin and alumina. 

Casein Sizing. — Casein is a nitrogenous substance occurring 
in milk and closely resembling animal albumen in its composition 



308 THE CHEMISTRY OF PAPER-MAKING. 

and properties. One thousand parts of normal milk contain, 
according to Fownes, 48.20 parts of casein. A closely similar 
body is found in tlie vegetable kingdom, notably in pease, beans 
and lentils, and is called vegetable casein or legumin. Liebig, 
indeed, considers the two materials identical, but doubt has been 
thrown upon this view by later investigators. The name casein is 
derived from the Latin one for cheese, which is formed in large 
part of casein, and which bears a close resemblance to it. 

Casein is prepared by coagulating the milk with dilute acid 
or with rennet, and washing the coagulum first with water, then 
with water containing a little acid, and finally with pure water 
again. It may then be brought down by drying to a friable 
mass, and usually appears in commerce as a dry granular powder 
of yellowish tinge. It dissolves readily in very weak alkaline 
solutions and is precipitated by many salts and especially by alum. 
The solution has not been used to any extent in this country for 
sizing paper, but experiments in this direction have been made by 
a number of German mills whose experience has been sufficiently 
favorable to warrant a trial of the material by American paper- 
makers. Its use depends upon the property possessed by casein 
of forming a bulky, gelatinous, insoluble compound with alum 
which adheres to the fibres and subsequently dries upon them, 
leaving the pores well filled. 

The casein in the form of a 20 per cent, to 50 per cent, solution is 
commonly added to the engine just as rosin size would be, or it may 
be mixed with the size in any desired proportion. In either case 
alum is afterwards added to effect the precipitation as in case of 
rosin size. Paper sized with casein is said to be much more elastic 
than that sized with rosin. Practically all of the casein goes into 
the sheet. Paper so sized has an especially good feel and readily 
takes a high finish. Casein size also lessens the objectionable dust 
which often comes from papers carrying a large amount of mineral 
matter, and the percentage of filler retained is greater than with 
rosin size. 

The most serious objection which has been raised against this 
material as a sizing agent, is that it is very liable, unless properly 
prepared and handled, to impart an unpleasant odor to the paper. 

Silicate of Soda. — This material has been used from time to 
time by mills which desired to obtain a very hard sized paper 
which should rattle. It is commonly received in the form of a 



SIZING AND LOADING. 309 

clear, very heavy liquid, containing about 50 per cent, of the sili- 
cate dissolved in water. It is strongly caustic and may be used 
for preparing size in place of the carbonate usually employed, or 
any desired quantity may be mixed with the size itself or added 
directly to the engine. The addition of alum determines the for- 
mation of a bulky, gelatinous precipitate of hydrated silicic acid 
which is very similar in appearance to precipitated alumina. The 
same precipitation is brought about by the addition of acid to 
the engine, but this procedure is liable to bring the silica down 
in a gritty or sandy condition in which it is likely to cause 
trouble in various ways, and especially by leaving the surface of 
the sheet dusty. The only important advantage which the use of 
silicate of soda offers, is that it produces a harder paper and its use 
is in this country confined in the main to mills making writing 
papers. 

Alum. — We have already pointed out (Part I., page 77,) that 
the term alum as employed in paper-making has come to refer 
almost entirely to sulphate of alumina, and we shall now use the 
word in this restricted sense. The use of alum in paper-making 
is due primarily to the fact that when a solution of alum comes in 
contact with one of rosin size, there is formed a bulky, adhesive, 
gelatinous precipitate, composed of alumina and rosin, which 
adheres to the fibres and dries down to a sort of water-repellent 
varnish. Other things being equal, the value of an alum for 
the purposes of paper-making is usually held to vary with the per- 
centage of alumina present, but this is by no means a conclusive 
indication of the sizing power. The accompanying table brings 
out the great variations which appear in the composition of com- 
mercial alums, and the sizing power of the several samples is influ- 
enced by many factors other than the mere percentage of alumina. 
It will be noted in reference to these analyses that in a well-made 
alum the proportion of material insoluble in water is rarely above 
0.50 per cent., and is often much below this figure. A much 
higher percentage, such as appears for instance in Samples VI., 
VIII., X., and XIV., generally indicates that the original raw 
material has not been thoroughly broken down by the acid. Such 
alums are apt to contain considerable free acid, and they find 
their chief use in bleaching or as a coagulant in the purification of 
water. They are only adapted for sizing in case of the cheap- 
est papers. The alumina in these analyses varies from 11.64 



310 



THE CHEMISTRY OF PAPER-MAKING. 



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SIZING AND LOADING. 311 

per cent, in Sample XII. , to 22.37 per cent, in Sample IX., but 
there is no corresponding variation in the sizing power. Sample 
IX. is a very basic alum, and it is doubtful if the excess of alumina 
above that needed to form the neutral sulphate has much, if any, 
sizing value. The large quantity of free acid in XII. of course 
decomposes its equivalent of size, and, although objectionable in 
itself, increases the apparent sizing power of the alum. The maxi- 
mum quantity of size is precipitated by XVI. with only 17.04 per 
cent, of alumina and no free acid, but after making proper allow- 
ance for the zinc and iron present in both cases, it appears that 
IX. is made up more largely of basic sulphate than the stronger 
XVI. 

The deleterious effect of iron upon color makes the amount of 
this constituent a matter of importance in any alum intended for 
use in the paper engine. The total amount of iron oxides in the 
samples under discussion ranges from 0.02 per cent, in Sample I. 
to 1.23 per cent, in the low grade Sample XII., and these figures 
may be taken as fairly representing the extremes. Since the salts 
of the protoxide of iron are comparatively colorless, it is the object 
of the alum manufacturer to convert as far as possible all the iron 
present to the ferrous state. This may be effected by the addi- 
tion of metallic zinc which liberates nascent hydrogen as it goes 
into solution in the liquid alum, and to this fact is due the pres- 
ence of the zinc oxide reported in certain analyses in the table. 
It should, however, be noted in this connection that while the 
color of an alum is improved by bringing the iron into the 
ferrous state, it does not follow that such iron is any the less 
objectionable, for it is rapidly oxidized during the processes of 
paper-making. 

The soda which appears as a common constituent of the alums 
in the table is by itself without significance as to their value or 
character. Its presence is explained partly by the use of bicar- 
bonate of soda in the manufacture of porous alums, and to neutral- 
ize the last portions of acid ; but in some cases it may be derived 
from cryolite when this is used as the raw material. 

The proportion of sulphuric acid deserves more attention than 
it usually receives from buyers of alum. Free acid, except on a 
bleaching alum, is objectionable not only because of its effect in 
color, but because it decomposes the size without at the same 
time precipitating alumina. If excessive quantities . of a strongly 



312 THE CHEMISTRY OF PAPER-MAKING. 

acid alum are used there is the further danger of attacking the 
wires and felts, and injuring the strength of the paper as it passes 
over the driers. 

From our own point of view a neutral, or slightly basic, alum 
should give the best results in sizing, but many paper-makers 
have a preference for a very basic or " concentrated " alum. Sam- 
ples XIII. and XL, which contain about the same amount of total 
acid, may be taken as representing the extremes in the proportion 
of acid to base. 

The amount of alum used in sizing ranges in ordinary practice 
from 6 to 12 lbs. to an engine carrying 500 lbs. A larger quantity 
is sometimes added if the sizing is to be very hard, but the usual 
amount is about 10 lbs. It is best to put the size in first and 
allow it to become thoroughly distributed through the stock before 
the addition of alum, but some mills reverse this process. There 
is danger in this event that the size will be precipitated in small 
lumps, which come to the surface and make spots in the paper. 
In making manila paper the dry alum is added directly to the 
engine, but for better papers a stock solution is made up and 
cleared by settling or straining. 

The quantity of alum used is always much in excess of that 
required to merely precipitate the size, but although there is a con- 
siderable waste of alum in most mills, good results in sizing cannot 
be obtained by use of the minimum amount of alum required 
by the size alone. A moderate proportion of free alum appears 
to be essential to good sizing, and portions of the alum added 
are neutralized by the water, by lime or other alkalis present in 
the stock, and by traces of bleach. By virtue of these decom- 
positions the alum in the engine has an important clearing action 
similar to that which occurs during its use in purifying water. 
That is, it has a tendency to coagulate or gather together the fine 
suspended matter of any kind, such as particles of filler or bits of 
fibre which have been too finely beaten so that they might other- 
wise be lost. 

Temperature has a noticeable effect on the quantity of alum 
required, particularly when ground wood is used, the amount 
required increasing with the rise in temperature. If the temper- 
ature of the contents of the engine exceeds 100° F. it is impossible 
to make a well-sized sheet, even though a large excess of alum be 
added. 



SIZING AND LOADING. 313 

Apart from its value as a sizing agent alum performs several 
important offices in the coloring of paper, and these will be con- 
sidered in the chapter on Coloring. 

Sizing with Acid Sulphites. — Numerous attempts have been 
made by German chemists to size paper by using bisulphite liquor 
in place of alum to effect the decomposition of the rosin soap. 
This decomposition with precipitation of rosin can easily be 
brought about in this way, the extra acid combining with the 
soda and setting free the rosin. When a lime liquor is used 
there is thus formed sulphite of soda and sulphite of lime. As 
the last-named compound is insoluble, it serves to increase the 
proportion of filler in the sheet. This method of sizing is very 
cheap, and it is claimed by Kellner to have the important advan- 
tage, when appried to papers containing ground wood, of prevent- 
ing or retarding very much the loss of color which usually takes 
place in such papers with age. This conclusion is rendered some- 
what doubtful by the researches of Herzberg upon the action of 
light upon rosin size, which indicate that the change which gives 
the darkening in color is not one of simple oxidation. The addi- 
tion of the sulphite liquor has. undoubtedly some bleaching action 
which may be useful in case of papers made for immediate con- 
sumption, but such bleaching action is a very fugitive one. There 
is, moreover, considerable danger that if too much of the liquor 
is added to the engine, some of the free sulphurous acid may be 
oxidized to sulphuric acid as the paper passes over the heated 
driers. Any such action at this point would not only rust the 
driers, but would be apt to render the paper brittle through 
formation of hydrocellulose. 

Any free sulphurous acid in the stock would corrode the wire 
as the sheet was formed on the machine. Another serious ob- 
jection to this method of sizing is found in the action of the sul- 
phurous acid upon many of the coloring matters which might be 
employed with it. It cannot be denied, in view of the results of 
Dr. Kellner and others, that this method of sizing, when properly 
controlled, may be made to yield good results at a comparatively 
low cost, but the process is one which is liable to involve in serious 
difficulty any less experienced workers. 

The Mitscherlich Sizing- Process. — Among the substances 
which occur in waste sulphite liquors are certain derivatives of 
the wood which are more or less closely allied to tannic acid, 



314 THE CHEMISTRY OF PAPER-MAKING. 

and which possess its property of precipitating gelatine. Dr. 
Mitscherlich has turned this to account in a process for engine- 
sizing with glue, and has made it a subject of a patent. In carry- 
ing out his process ordinary glue is digested at a temperature of 
about 60°, with ten times its weight of waste sulphite liquor, until 
dissolved. This requires several hours, and the mixture should be 
stirred from time to time. The solution thus prepared is then 
diluted with more waste liquor until the proportion of liquid to glue 
is about 50 to 1. The admixture must be made very gradually 
with constant stirring, and at the ordinary temperature of the air. 
The glue combines with the astringent material of the liquor to 
the extent of about 60 per cent, of its own weight, and is precipi- 
tated in flocks. The whole mixture is then allowed to stand for 
twenty-four hours. The liquor is then decanted from the precipi- 
tate, and the latter mixed with a quantity of water weighing 
about forty times as much as the glue originally taken. A small 
quantity of chalk or soda-ash, or other substances capable of 
neutralizing the free acid, is then added. The compound of 
glue and astringent matter goes into solution quickly, and a 
liquor so prepared may be added directly to the engine for 
use in size. Alum, or a weak acid, will then cause the pre- 
cipitation of the gelatine compound throughout the fibre, and the 
solution may be therefore used when desired in connection with 
ordinary size. 

The process just described is a development of the one first 
patented by Dr. Mitscherlich in 1886, in which paper was sized by 
feeding in continuously on one side of the beating engine the 
waste sulphite liquor in a small stream, while ordinary glue solu- 
tion was similarly fed in on the other side of the engine. As the 
two dilute solutions came together the gelatine compound was 
precipitated, and the action was, of course, continuous as long as 
the supply was kept up. 

Loading. — The use of mineral fillers has come to have a recog- 
nized and legitimate place in paper-making, and the presence of 
such fillers in a sheet is not under ordinary circumstances to be 
regarded as evidence of adulteration. They are used quite as 
much for their beneficial effect upon the feel and finish of the 
paper as through a desire to lower the cost of production. Many 
of the best grades of book paper could not be made at all with- 
out the use of some filler in considerable amount to give the 



4 ■'.- 

/^; ;■:/■'-■ ^-. \ ■■■;.■ ;v 




Fig. 66. — South Carolina Clay. 



/<; 



Fig. 67. — English China Clay. 



SIZING AND LOADING. 315 

smoothness of surface required to bring out the fine lines of 
process cuts. 

The materials commonly employed in this connection are some 
of the better sorts of china clay or kaolin, ground talc, and 
sulphate of lime. In preparing these for the paper-maker the clays 
are mixed with water to form a thin cream, which is then sent 
through long sluice ways or settling boxes with riffles to catch and 
retain the coarser particles which settle out. The water is then 
allowed to drain off from the finest particles, which alone are suit- 
able for paper-making, and the clay comes to the market in the 
form of fairly dry lumps of moderate size. 

The ground talc is usually not floated, but it is put instead 
through a fine bolting cloth. Sulphate of lime when used in the 
form of ground gypsum is similarly treated. 

The value of the filling material for use in paper-making is 
dependent upon several factors, those of most importance being 
color and fineness. The suitability of the material is also largely 
determined by its specific gravity, as this of course affects the rate 
at which the particles of filler settle. The retention is thus likely 
to be low in case of a very heavy filler, and the paper is likely 
to be thin for weight. Solubility in water to any considerable 
extent of course unfits a material for use as a filler. Even the 
slight degree of solubility possessed by sulphate of lime is suffi- 
cient to cut down the retention appreciably. 

A filler for use in high-grade papers should be almost entirely 
free from either grit or mica, since the former is apt to mark the 
calender rolls, while the shiny specks of the latter are very appar- 
ent in the finished sheet. 

Clays. — These are formed by the weathering and disintegration 
of feldspathic rocks. The presence of mica indicates that the 
source of the clay was granite. With a moderate quantity of 
water they form a sticky plastic mass, with more or less soapy 
feel. Chemically considered they are essentially silicate of alu- 
mina. Since the value of clay for the uses of paper-making is so 
largely determined by color, only those sorts like the china clays, 
in which the content of iron is small, are suitable. The com- 
position of the clays in general use by paper-makers is given 
below, and their microscopical appearance is shown in Figs. 6Q, 
67, and 68. 



316 



THE CHEMISTRY OF PAPER-MAKING. 



Analyses of Clays. 
Griffin & Little. 



Moisture, loss at 100° C 

Combined water, volatile at red heat 

Silica (Si0 2 ) 

Alumina (A1 2 3 ) 

Sesquioxide of iron (Fe 2 3 ) . 

Lime (CaO) 

Magnesia (MgO) 

Alkalis 



0.30 

12.27 

47.56 

38.12 

0.08 

0.39 

0.00 

1.28 



II. 



10.15 

10.77 

42.72 

33.44 

1.04 

1.61 

0.16 

0.11 



7.09 
11.27 
43.50 

35.48 

trace. 

0.17 

0.41 

2.08 



IV. 



9.10 

12.79 

41.16 

35.84 

0.67 

0.42 

0.02 



100.00 



100.00 



100.00 



100.00 



Specific gravity of dry substance 
Grit by flotation test (per cent.) 



2.8625 
0.65 



2.5585 
6.83 



2.5451 
0.10 



Agalite. — This is a finely ground talc, and is, chemically, a 
silicate of magnesia. It has an especially good color, and a smooth, 
soapy feel. It is not nearty so finely reduced as clay, and the 
proportion of grit is much larger. It is, however, retained well 
in the paper, and large quantities of it are used. Its appearance 
under the microscope is shown in Fig. 69. 



Analysis of Agalite. 

Griffin & Little. 

Per cent. 

Moisture and combined water, volatile 

at red heat 1.40 

Silica (Si0 2 ) 61.89 

Alumina (A1 2 3 ) 1.36 

Sesquioxide of iron (Fe 2 3 ) 0.44 

Lime (CaO) 4.21 

Magnesia (MgO) . . . . . . . . 30.70 

100.10 

Specific gravity, 2.6875. 

Pearl Hardening. — Crystallized sulphate of lime, CaS0 4 , 
2H 2 0, prepared by precipitating a solution of calcium chloride 
with one of acid sodium sulphate, or with dilute sulphuric acid, 



"-• 




Fig. 68. — Leamour Clay. 



Iv 



m^\ 






Fig. 69. — Agalite. 



SIZING AND LOADING. 317 

has been largely imported, and used as a filler in the finer grades 
of paper under the name of Pearl hardening. Abroad it is some- 
times called Annaline. Grown filler is another trade name for the 
same material. 

The crystallized sulphate thus prepared is especially white, 
clean, and free from grit. As found in the market, in moist 
lumps, it contains a considerable percentage of water in addition 
to the water of crystallization. The latter amounts to 20.93 per 
cent, on the chemically pure, and otherwise dry, substance ; and 
this combined water remains with the filler to add to the weight 
of the air-dry paper. We give the following 

Analysis of Peakl Hardening. 

Griffin & Little. 

Per cent. 

Sand, etc., insoluble in acid None. 

Moisture 25.99 

Combined water, driven off at red heat . 15.31 

Sulphate of lime (CaS0 4 ) 1 57.85 

Chloride of calcium (CaCl 2 ) 0.79 

99.94 

Specific gravity of dry material, 2.3962. 

Under the microscope, Fig. 70, pearl hardening is seen to consist 
of minute needle-like crystals which have somewhat the appear- 
ance of short fibres. The crystals are soluble in about 400 parts 
of water, or to the extent of about 22 lbs. per 1000 gals. This 
fact, especially when the proportion of filler used is small, and 
when the return water is allowed to run away, has a considerable 
effect in cutting down retention. 

Ground Gypsum is sometimes, though rarely, used as a filler. 
It answers to the same formula as pearl hardening, CaS0 4 , 2H 2 0, 
but in the grinding its crystalline structure is broken down, so 
that, in this regard, it is little different from any other finely 
pulverized mineral. 

Fibrous Alumine. — A new filler, which has several important 
advantages, has lately been put upon the market under this name. 

1 Equivalent to crystallized sulphate of lime (CaS0 4 , 2H 2 0), 72.89. 



318 



THE CHEMISTRY OF PAPER-MAKING. 



It is a fine, smooth, white powder almost entirely free from grit, 
and has the following composition : — 



Analysis of Fibrous Alumine. 
Griffin & Little. 



Insoluble in acid 

Sulphate of lime (CaS0 4 ) * . . 
Sulphate of alumina (A1 2 (S0 4 ) 3 ) 
Sulphate of iron (Fe 2 (S0 4 ) 3 ) • 
Carbonate of lime (CaC0 3 ) . . 
Carbonate of magnesia (MgC0 3 ) 
Combined water . . . . . . 



Per cent. 

0.32 
82.55 
5.92 
0.22 
1.04 
0.34 
9.67 



100.06 

1 Equivalent to crystallized sulphate of lime (CaS0 4 , 2H 2 0), 104.40. 

Examination of the above analysis discloses the fact that the 
filler consists mainly of anhydrous sulphate of lime and that the 
alumina present is also combined as sulphate. This sulphate of 
alumina is, therefore, as readily available for use in sizing as though 
it were so much alum added directly to the engine. Upon agita- 
tion with water the anhydrous sulphate of lime combines with 
two molecules of water of crystallization, and assumes the fibrous, 
crystalline structure which is shown in Fig. 71, and from which 
the filler derives its name. Every 100 lbs. of the sulphate of lime 
as put in the engine forms 126 lbs. of the crystallized sul- 
phate, and this fact, together with the fibrous character of the 
crystals, has an important bearing upon the quantity retained. 
Our comparative tests have shown that after hydration fibrous 
alumine settles much more slowly than other mineral fillers, and 
this not only aids retention but ensures a more even distribution 
of the filler through the paper. The sizing power of 100 lbs. 
of fibrous alumine is about equal to that of 12 lbs. of alum of 
good grade. 

Retention. — Fillers are usually added to the engine after the 
stock has been well beaten, and before the addition of the size and 
alum, as the precipitation of the size tends to fix the filler in the 
fibre. Clays are made into a cream with water, and when intended 
for the better grades of paper are strained through a piece of 
Fourdrinier wire before going to the engine. Pearl hardening is 





\, 



V 



Fig. 70. — Pearl Hardening. 



Fig. 71. — Fibrous Alumine. 



SIZING AND LOADING. 319 

similarly beaten up, although the straining is unnecessary. Agalite 
is put into the engine dry. Fibrous aluraine is agitated briskly in 
a separate vessel with water for about one-half hour to bring about 
the desired crystallization, and is then run into the engine through 
a revolving strainer which holds back any of the larger crystals. 

The quantity of filler retained by the paper may vary from 30 to 
80 per cent, of that introduced into the engine. The higher figure 
is only reached under exceptional conditions, and a retention of 
50 per cent, is usually regarded as satisfactory. A number of 
factors influence the retention, but although it is easy to point out 
in a general way the direction of their effect, it is impossible to lay 
down rules which shall apply to any one factor while the others 
are ignored. The kind of stock and the thoroughness with which 
it has been beaten and sized has much to do with the quantity of 
filler left in the sheet. Slow stuff holds the filler much better than 
that which is " quick " and allows the water to leave it rapidly on 
the wire. A heavy pull on the suction-boxes cuts down retention, 
and there is also, of course, a heavy loss in the return water when 
this is allowed to run to waste. This may amount to a pound of 
filler in every 30 gallons. Thick stuff and heavy papers generally 
show better retention than thin papers or stuff which is much 
diluted, and the percentage held varies also with the different 
fillers and the quantities used. With pearl hardening, for example, 
the proportion retained is usually greater when the quantity used 
is large than when it is inconsiderable. 

Use of Starcli. — J. Wiesner, who has examined some hundreds 
of ancient papers, finds that prior to the 13th century starch was 
the only material used for sizing. It is still used in small quanti- 
ties as a filler and is thought to give a better feel and surface to 
the paper. It is either boiled up with the size or the boiled paste 
may be added directly to the engine. Often the starch is merely 
mixed with water and added after the mineral filler. Its value ' is 
doubtful, as many tests prove the retention to be extremely low. 



320 THE CHEMISTRY OF PAPER-MAKING. 



CHAPTER VI. 

COLORING. 

The great advances in textile-dyeing and color-printing which 
have resulted from the application of modern chemical methods of 
research to the problems of the art have by no means found their 
counterpart in the coloring of paper, which still remains a rather 
crude and empirical operation. Men whose knowledge of the dif- 
ferent coloring-matters and the methods for their development or 
application is in any way coextensive with that of the best textile 
dyers are almost unknown in the paper trade. The coloring of an 
engine of stock is usually only a minor detail in the work of a 
busy superintendent, although brightness and evenness of color 
are among the most important factors in determining the quality 
of his product. 

The term " color " as used in paper-making is applied much more 
generally to those nice distinctions in shade, tint, and general 
appearance which are to be observed in papers of the same class 
than to the actual color of the sheet in the ordinary sense of the 
word. 

The materials directly concerned in coloring may be roughly 
classified as pigments and dyes. Pigments, of which ultramarine 
may be taken as a type, consist of fine, insoluble, intensely col- 
ored particles which are distributed through the sheet in quantity 
sufficient to give the desired tint. Dyes must, from their nature, 
be soluble until they are fixed or developed upon the fibre either 
by entering into loose combination with the substance of the fibre 
or through the intermediate action of some material called a mor- 
dant which has an affinity for both the fibre and the dye. 

Dyes which are taken up by the fibre without a mordant are 
called substantive colors, while those which need a mordant are 
termed adjective colors. The classification is usually made with 
reference to silk or wool, as these fibres have much more affinity 
for colors than those of vegetable origin. 

The number of pigments used by paper-makers is quite limited, 



COLORING. 321 



and most of these are referred to in Chapter VIII. under Mineral 
Colors. The pigments may either be added directly to the stock 
in the engine, as in case of ultramarine, orange mineral, and Vene- 
tian red, or they may be formed upon the fibre, as when chrome yel- 
low is produced by the addition of a solution of bichromate of 
potash followed by one of sugar of lead. 

Prussian blue was at one time always made at the mill by mix- 
ing a solution of copperas with, one of yellow prussiate of potash, 
washing the precipitated color by decantation and oxidizing, either 
by exposure to the air or by addition of a solution of bleaching- 
powder. Prussian blue is apt to give a greenish tint to the paper, 
and should always be added after the alum and before the size, as 
the color is discharged by alkalis. 

The complex and peculiar pigment known as ultramarine is 
largely used in paper-making, and the term is always understood 
to apply to the blue pigment, although red, green, yellow, and 
violet ultramarines are known. Common ultramarine often has 
a greenish cast. The color of a sample of the pigment is always 
made darker by moisture, and for this reason the low grades some- 
times contain added water, glycerine, or molasses. They are 
lightened in color by admixture of clay, or sulphate of lime, or 
sulphate of barium. 

Ultramarine is very sensitive to acid and to acid alums, but the 
different samples vary considerably in their power to withstand 
this action without loss of color. A little red is commonly used 
with the pigment to improve the shade. Owing to the difficulty 
of thoroughly wetting a dry powder, it is well to mix the ultra- 
marine with a little glycerine, and to dilute with water before 
adding to the paper engine. Spots due to small lumps of the 
powder which break up under the calender rolls are otherwise 
likely to appear. 

The yellow pigments are chromate of lead and yellow ochre. 
The former is used either as canary paste, or as a powder, but 
most commonly it is formed on the fibre in the engine. For this 
purpose a solution of bichromate of potash is added to the stock, 
and ten or fifteen minutes later one of sugar of lead. The usual 
proportion is one pound of bichromate to every two pounds of the 
lead salt. Alums, whether basic or acid, have no effect upon 
chrome yellow, but bleach residues and alkalis give it an orange 
tone, which may with sufficient alkali pass to red. The pigment 



322 THE CHEMISTBY OF PAPER-MAKING. 

is much used with blues to form green. With Venetian red it 
gives an orange. 

Dyes. — Cochineal as a coloring-matter has been used for a very 
long time for tinting papers rose or scarlet. The dye is not so 
durable as some others of the same nature, but is of exceptional 
purity and of rare brilliance. It is most frequently used along 
with ultramarine or other blues, for whitening pulp in the produc- 
tion of high-class papers. Since the discovery of the coal-tar 
colors the use of cochineal has been largely superseded by fuch- 
sine, or magenta, or eosin. Notwithstanding this, there are cir- 
cumstances under which cochineal is still used, yielding rose, 
pink, or scarlet colors of any depth of shade, and remarkably 
pleasing to the eye. Its cost, judged from the standpoint of 
tinctorial power, is greater than other dyes of the same color, 
more especially those belonging to the aniline series. 

Cochineal, as is well known, is the body of an insect found in 
Mexico and other parts of Central America, and is therefore, per- 
haps, the only dye of animal origin known to dyers. Although 
it was originally found in the central part of the American con- 
tinent, successful attempts have been made to cultivate its growth 
in other hot countries ; hence large consignments are sent to Eng- 
land and other parts of Europe, from Algeria, Teneriffe, Madeira, 
etc. The female insects, which yield a larger amount of coloring- 
matter than the males, are carefully gathered from the cactus 
plant, upon which they live, and are killed by roasting in a stove 
or by exposure on plates in the sun. The dried flies are then 
rubbed, sieved to free them from dirt, and finally sorted. The 
larger grained variety is the best. They present a somewhat 
shrivelled appearance of a dark brownish red color with frequent 
patches of a silvery lustre. 

The coloring-matter contained in cochineal is called carminic 
acid. The behavior of this carminic acid toward chemical salts, 
etc., shows the paper-maker very clearly the various reactions 
which take place in the beater engine under the circumstances 
which usually prevail there, and therefore it is important that 
these reactions be known, so that he can regulate the shade and 
otherwise produce in the sheet of paper to be made, a good, clear 
color of uniform brilliant appearance. The aqueous extract of 
cochineal is a deep red liquid, which color is transformed into a 
deep violet on the addition of lime-water, while the addition of 



COLORING. 323 



a solution of acetate of lead causes a deep violet blue lake 
to separate out in the form of a precipitate. If a solution of 
alum, cream of tartar, or acid oxalate of potash be added to it, the 
albuminous substance which is dissolved along with the coloring- 
matter from the flies, coagulates and carries down the carminic 
acid as a flocculent precipitate of a beautiful deep carmine color. 
This is the purest and strongest carmine. It is of great coloring- 
power, and in order to weaken it for industrial purposes, it is 
mixed with colorless substances, such as starch. 

When carminic acid is separated from aqueous decoctions of 
cochineal by means of metallic oxides, the compounds formed are 
called carmine lakes. Thus, when an 'alkaline carbonate (carbon- 
ate of soda) dissolved in water is added to a decoction of cochineal 
which contains alum, a beautiful colored compound of the car- 
minic acid and the alumina of the alum separates out, which is 
essentially a carmine lake. In the same way, when " tin crys- 
tals," previously dissolved in water, are added to a slightly alka- 
line decoction of cochineal, the oxide of tin combines with the 
carminic acid, forming, as above, a beautiful carmine lake. The 
aqueous extract of cochineal is unaltered by the addition of very 
dilute acids. Alkalis, on the other hand, change the original 
crimson to a bluish red. These reactions show, in a general way, 
what will take place should any of these chemicals be brought 
into contact with the color when in the beater. An excess of free 
alkali (rosin size), for example, will impart a bluish shade to the 
pulp. 

There are two decoctions of cochineal used when tinting papers 
with this dye ; namely, the aqueous and ammoniacal extracts. The 
former is simply prepared by grinding the cochineal flies to powder 
in a large mortar and gently boiling them in pure soft water for 
naif an hour in an ordinary copper. The first extract is then 
drawn off, and the boiling repeated several times with fresh 
portions of water. The extracts are then mixed and carefully 
filtered through a close cotton bag. 

The ammoniacal extract is prepared by adding a known weight 
of the pulverized dye to spirits of ammonia in a carboy, with 
constant stirring, the proportions being 10 lbs. of cochineal to 
three gallons of ammonia liquor of QQ per cent. The carboy and 
contents are then closely corked up and laid aside for several days 
in a warm room, the temperature of which is kept constant until 



324 THE CHEMISTBY OF PAPER-MAKING. 

the liquor has thickened. The longer it is kept, the better its 
quality. Before adding this extract to the pulp in the beater, it 
must be diluted with water and carefully filtered. 

Pulp which has been mordanted with alum and covered with 
cochineal produces a more durable tone than pulp not mordanted 
at all. But the color is somewhat dull, and is brightened by the 
use of a little oxalic acid. This acid imparts a yellowish shade to 
the crimson, especially if much of it be used. The presence of an 
excess of alkali (rosin size) changes the tone from red to blue, and 
therefore the size must not be in excess. Indeed, when sizing, the 
alum or sulphate of alumina must be added until the characteristic 
blue, produced by the alkali, has vanished. An addition of " tin 
crystals " brightens the color and develops its full brilliance. A 
much better reagent to use for the development and "fixing" of 
cochineal colors is the mordant known in trade as " scarlet liquor," 
and which is so extensively used in the dyeing and calico-printing 
industries. Scarlet liquor is a chloride of tin specially prepared in 
the liquid form and sold in carboys. Its action upon the pulp in 
the beater is much surer and quicker than "tin crystals," and 
on this account is to be preferred. A small quantity of tartaric 
acid is used along with it. 

With the aqueous extract of cochineal it is somewhat difficult 
to obtain uniform results, and for this reason it is better to employ 
the ammoniacal extract, which, in conjunction with alum and tar- 
taric acid, is the best way of coloring paper pulp with this dye. 
The alum and tartaric acid neutralize the ammoniacal cochineal 
and precipitate the carmine lake upon the pulp in a very uniform 
state. The pulp for this purpose should be well washed and free 
from bleach liquor. The alum and tartaric acid are then added, 
and when thoroughly incorporated with the fibre the ammoniacal 
cochineal is poured in in sufficient quantity to produce the depth 
of color required. Tin crystals slightly acidified with muriatic 
acid improve and brighten the color. 

When coloring with this dye the " sizing " must be carried out 
with care. The pulp is usually colored before adding the size. 
The alum may then be added, and when thoroughly mixed, the 
rosin size, which should be largely diluted with water, is grad- 
ually poured in. The reason of this is obvious. If the. size be 
added in the strong and concentrated state, the precipitated flakes 
of rosin may surround portions of the colored pulp, changing them 



COLORING. 325 

to blue, which may not be affected by the acidity of the alum, 
even though this is in excess. For this reason the pulp is kept 
distinctly acid, with alum or the other mordants used, before run- 
ning it into the stuff chest. 

Papers colored with cochineal are very easily bleached by chlo- 
rine or bleach liquor, and are very susceptible to change under the 
influence of alkalis and acids. When heated in lime-water the 
crimson changes to violet. Dilute oil of vitriol transforms it into 
orange. Alcohol acidified with muriatic acid changes the color 
into a dirty yellow, while chloride of copper converts it into brown. 
By these tests cochineal colors may be known. 

Since the discovery, by Perkins, in 1856, of mauvein, the list of 
materials available for the purposes of the dyer and paper-stainer 
has been enriched by a long series of very complex synthetical 
products derived from coal tar and known collectively as the coal- 
tar colors. These are generally the salts, as the hydrochloride or 
acetate, of colorless bases. For a time they were in some disre- 
pute because of their want of fastness, but, as now made, some of 
them are more fast than indigo, while their brilliancy and con- 
venience have enabled them to largely displace the older coloring- 
materials. The two most prominent classes of these dyes are those 
derived from aniline and the more recent azo dyes, which last form 
a whole series of fast and brilliant colors, all containing nitrogen. 

As the study of the coal-tar colors forms one of the most difficult 
branches of chemistry, owing to their immense number and great 
complexity of composition, no attempt can be made in the present 
chapter to do more than refer, under their commercial names, to a 
few of those more commonly employed in paper-making. 

The more prominent red dyes are magenta, eosin, the fast pinks, 
and safranine. These are called "straight colors," and many 
shades are made by their proper blending. They are mordanted 
with alum, or some extract like fustic containing tannin, or they 
may be fixed by sugar of lead. The magentas are salts of rosani- 
line, the hydrochloride being a common form, and they are also 
known commercially as fuchsinc and aniline red. They occur as 
brilliant green crystals having the sheen noticed on the backs of 
certain beetles. The blue shades are purest, and well-crystallized 
samples should be preferred. They sometimes contain arsenic as 
an impurity. They dissolve readily in water to a magnificent 
crimson solution. 



326 THE CHEMISTRY OF PAPER-MAKING. 

The eosins are a class of dyes derived from fluorescein. They 
are soluble in water and in alcohol, the latter solution being com- 
monly fluorescent. They give a red which in some instances 
inclines to blue. They form lakes with alum. 

Commercial safranine is a reddish-brown powder, which forms 
with water a red solution from which the color may be fixed by 
tannin extracts or tartar emetic. Under the head of the safranine 
dyes are comprised, however, a class of colors which range in shade 
from red to blue. 

For the browns between red and yellow, paper brown and Bis- 
marck brown are among the colors used, the tint being thrown 
to one side or the other by careful admixture of reds or yellows. 
These browns are soluble in water, and are best mordanted by 
means of tartar emetic. 

Auramine and naphthol are among the principal yellow dyes. 
The former occurs as a sulphur-yellow powder, soluble in water 
and alcohol. It may be fixed by tartar emetic or by tannin. 

The green coloring-matters derived from coal tar are especially 
rich and numerous. The straight colors, brilliant green, Victoria 
green, and malachite green, are those most used, and all three are 
soluble in water. 

The blue dyes are also numerous, but the three most generally 
employed are soluble blue, paper blue, and cotton blue. Special 
shades are obtained in commercial anilines by the admixture of 
two or more of these. All are fixed by alum. 

Methyl violet is the color most used for violet and the reddish 
shades of blue. It occurs as a greenish powder or in crystals. 
The tint of the commercial samples is made to range from very 
red to very blue. The color is precipitated by yellow prussiate 
of potash. 

The commercial dyes which give the intermediate shades and 
colors are frequently, as has been already indicated, made by 
mixing two or more of the straight colors in proportions deter- 
mined by careful experiment. Such admixture may often be 
detected by allowing a drop of the solution to fall upon filter 
paper, when, as the drop spreads out, differently colored zones 
appear. It is, in many cases, not difficult to match such a sample 
of mixed color by making up a solution containing a given quan- 
tity of the sample for a standard, and then mixing together, in 
carefully noted quantities, solutions of the other dyes which seem 



COLORING. 327 



to be required, until the standard solution has been matched. 
From the strength and quantities of the other solutions used may 
then be calculated the proportions needed of the different dyes. All 
the solutions are best made rather dilute, and the tints are most 
easily compared in tubes such as are used for nesslerizing water. 

The intense coloring power of these dyes makes them especially 
liable to adulteration or dilution by inert and valueless, materials. 
Sugar, dextrine, common salt, and sulphate of soda are commonly 
used for this purpose and are for the most part unobjectionable, 
except as they may carry dirt or diminish the tinctorial power of 
the sample. The salt and sulphate of soda, Glauber's salt, have a 
certain value as mordants, but when required they can be bought 
more cheaply under their common names. This sophistication has 
been the direct result of the demand by the buyers for cheap 
colors, and it may be taken as a general rule that the best colors 
will be found the cheapest when the cost is estimated, as it should 
be, on the ton of paper colored. 

For use in the paper engine, it is customary to select those colors 
which are soluble in water, as the use of the alcohol colors involves 
considerable extra expense. The best colors will stand boiling; 
those of lower grade should be dissolved in hot water. The solu- 
tion, in either case, should be carefully strained through flannel 
and added to the engine before the size or alum. Many of the 
color manufacturers send out special formulas for guidance in the 
use of their colors, and it is well to consult and follow these. When 
the color has been properly fixed, either by the fibre or by the use 
of alum or other mordant, there should be no tinge to the water 
which runs away when a handful of the stuff is squeezed. It will 
be commonly found that the tints obtained from a given color will 
vary with the furnish, since the different fibres take the color dif- 
ferently. Ground wood is especially apt to change the tone of a 
color, but it is in any case impossible to lay down general rules 
which can replace experience. 

The coloring of paper to the exact shade required by the buyer 
is somewhat complicated by the fact that the color of the stuff in 
the beater is never that of the finished paper, but always darker, 
mainly because of the large amount of water present, but also in 
some cases because of the effect which the heat of the dryers has 
upon certain delicate colors. It is, for this reason, often custom- 
ary for superintendents to reduce to pulp the sheet they wish to 



328 THE CHEMISTRY OF PAPER-MAKING. 

match, and then to bring the stuff in the engine to this shade. By 
folding a sheet and looking into it, as into a partly opened book, 
the intensity of a faint tint is much increased, through multiple 
reflection of the light, and in this way a conclusion may often be 
reached as to the colors required to match the given shade. 

A rough idea of what the color of the finished sheet will be may 
be obtained by squeezing a handful of the stuff and then -beating 
it out between the hands and drying, but the thickness and uneven- 
ness of the cake introduce a considerable chance for error. When 
several engines of a given color have to be made up, it is a common 
practice to retain a bowl of the stuff from the first engine and to 
use this as the standard for comparison. The color of the stuff 
in the bowl is, however, apt to change on standing, and especially 
to grow darker. The better way is to squeeze out a handful of 
the stuff and match the next engine by it, the sample from the 
second engine then serving for the following one, and so on. 
Since it is a difficult thing at best to secure an exact match be- 
tween two lots of paper, every care should be taken to have the 
conditions under which comparisons of color are made as nearly 
alike every time as possible. The character of the light coming 
through one window may be so far different from that at another 
one as to cause appreciable difference in the tint of colors examined 
at one place or the other. Light from the north is best. 

Great differences in light are caused by reflection from the 
objects outside, and it is therefore advisable to select some one 
place in the mill where the light is good, and to do all the match- 
ing there. At night an arc light is best for showing colors, but 
wherever possible a change of colors should only be made in the 
daytime. 

The kind of filler used has a considerable influence on the color 
of the sheet, and when changing onto a new filler or modifying the 
proportions of the old one it often becomes necessary to change 
the color furnish. The same observations of course apply when the 
mixture in the engine is modified by the addition of broken paper. 

Numerous color furnishes are given by Dunbar, — The Practical 
Paper-Maker, London, 1887, — which will be found useful as 
indicating the proportions in which the various coloring-matters 
are employed in the production of colored papers. In the use of 
such general recipes, however, due allowance must always be made 
for the character of the stock and other materials in the furnish. 



WATER. 329 



CHAPTER VII. 

WATER. 

The very large quantities of water which are required in the 
processes of paper-making, and the readiness with which the qual- 
ity of the product is influenced by conditions which affect the 
character of the water-supply, make the subject one of the first 
importance to the manufacturer. Water which is pure in the 
strict chemical sense — that is, water which contains no foreign 
substance — is never obtained in nature, so that, from the manu- 
facturing as well as from the sanitary standpoint, we have to 
consider waters with reference to the amount and character of 
the foreign constituents which they contain, and these include 
not only the mineral or inorganic substances which may be 
present, but also the various minute' forms of plant and animal 
life. 

Waters are broadly divided into surface and ground waters, 
surface waters comprising those of brooks, rivers, ponds, and 
lakes, while ground waters, as their name implies, are those which 
have percolated to some depth through the soil and the underly- 
ing porous strata. Although all these waters have a common 
origin in rain, and though surface waters become ground waters, 
and the reverse, there are yet certain broad distinctions between 
the classes, which are the result, in the main, of the action of light 
and air in the one case, and of the filtering and oxidizing power of 
porous earth, together with the solvent action of the water, in the 
other. Surface waters are apt to be more or less highly colored, 
and they contain plant and animal life, to which, in fact, much of 
their color is often due. Ground waters are clear and colorless, 
but they show a greater content of mineral matter. 

Soft waters are such as contain comparatively little of those 
mineral constituents which have the power of decomposing soap, 
while hard waters are those in which this power is present in 
a marked degree. Lime salts are the most common cause of 
hardness in water, and of these the carbonate is most conspicuous, 



330 THE CHEMISTRY OF PAPER-MAKING. 

although in some localities hardness may be due to sulphate. 
Common salt and salts of magnesium, when present, have the 
same effect, the latter to an extent which is even more marked 
than in case of those of lime. The hardness of a water, as deter- 
mined by the quantity of standard soap solution required to pro- 
duce a permanent lather, is expressed in degrees, each degree 
indicating a hardness equivalent to that due to one grain of 
carbonate of lime in a gallon of water, or, better, one part of 
carbonate of lime to 100,000 parts of water. 

For washing stock and for boiler purposes, a soft water is desir- 
able, or even necessary, from its greater solvent power in the one 
case, and its slight tendency to form scale in the other. Its 
importance in the other departments of the manufacture is rather 
overestimated; for in boiling stock, bleaching, or furnishing an 
engine, the softest water is made hard by the materials employed 
in the operation. The use of a very hard water will, however, 
undoubtedly increase the quantity of size required, since the size 
is merely a soap, and the insoluble lime or magnesia soaps thrown 
clown have little or no sizing power. Hardness due to sulphate 
of lime will also discharge the color of certain aniline blues, 
when these are used in the small amounts required in white 
papers. 

The most important quality of water, from the paper-maker's 
standpoint, is that of color. The volume of water used in making 
a ton of paper is so great, — it is probably never less than 50,000, 
and sometimes as much as 200,000, gallons, — and the fibres form 
so perfect a filter, besides possessing the power of removing much 
of the dissolved coloring-matter, that the presence in the water 
of even minute quantities of material injurious to color may render 
impossible the manufacture of paper of high grade. 

The purest natural waters are clear and colorless when exam- 
ined in small quantities, but in the mass they have a bluish tint. 
Surface waters show every gradation in color, from this pellucid 
clearness through yellow and reddish tints to the dark brown of 
swamp waters. The only systematic attempt, within our knowl- 
edge, to apply a standard to the measurement of the depth of 
color found in waters, has been made by Dr. Drown, chemist to 
the State Board of Health of Massachusetts, in the course of his 
exhaustive examination of the water-supplies of the State. The 
method adopted was that first suggested by Prof. Leeds. In the 



WATER. 331 

reports of the Board the color of the waters is expressed by num- 
bers which increase with the amount of color. Water having a 
color of 1.0 is a decided yellowish brown. This color corresponds 
to that obtained by nesslerizing 1 c.c. of the standard ammonium 
chloride solution used in the determination of the ammonia in 
water. By this standard the average depth of color of the Con- 
necticut River water at Turner's Falls is 0.30, though it ranges 
from 0.10 to 0.80. The Merrimac River at Lawrence shows a 
somewhat higher average, — 0.33, — though no single sample had 
a color above 0.70. 

The color of water is due mainly to those substances which 
leach out from the ulmic matter formed by the decay of leaves, 
grasses, and similar material in the soil or on the surface of the 
ground. In other words, the cause in most cases or in greater 
part is decaying vegetation. If this decay has proceeded far, as 
in peaty swamps, the brown coloration thus derived is very per- 
manent in character. 

The immense number of microscopic plants which are developed 
in some surface waters at certain seasons of the year are an impor- 
tant cause of color in such waters. Such growths are most com- 
mon in summer, though the periods of greatest abundance are 
often not coincident in case of the different genera. As a rule, 
however, the more important genera appear year after year in 
much the same order, so that where a particular organism has 
caused trouble at one time, a recurrence of the difficulty at about 
the same time may be expected the following year, if the condi- 
tions remain the same. The most important of these plants, from 
our present point of view, are the algee. These are green or bluish 
green, and, like the larger plants, derive their color from chloro- 
phyl and require light for their development. They do not occur 
to any extent in rapidly flowing streams, but thrive in ponds or 
reservoirs in which the water is comparatively stagnant. The 
fresh-water sponges, which occur as thin incrustations upon objects 
immersed in the water, or as a coating within the pipes, are doubt- 
less, through their decomposition, a not infrequent cause of unpleas- 
ant tastes and odors in water. They thrive best in summer and 
in water which is in motion. 

The suspended mineral matter, clay, silt, and such material, 
which a water carries has at times a marked effect upon the color 
of the water. This factor is a very variable one, and exerts its 



332 THE CHEMISTRY OF PAPER-MAKING. 

greatest influence after heavy rains, which wash the finely divided 
soil and earth into the streams. The soluble mineral constituents 
have, for the most part, no effect upon color. Even the soluble 
salts of iron are rarely or never present in amount sufficient to 
perceptibly color the water while they are present as such. It is 
when from any cause the iron is precipitated as hydrate that they 
cause trouble. 

We have occasionally noticed, in case of mills using unfiltered 
water drawn from ponds, a gradual accumulation of a rust-like 
deposit in the water pipes, which sometimes was sufficient to 
nearly choke them up. It is probable that this difficulty is due 
to the microscopical plants known as iron bacteria, of which the 
commonest and most important is Crenothrix Kuhniana, or "well- 
thread." Although perhaps the largest among the bacteria, it is 
of course exceedingly minute, and quite invisible to the naked eye, 
until, by the accumulation of multitudes of cells, flocks or masses 
of visible size are formed. The cells are mainly cylindrical, and 
are united end to end to form threads or filaments. The presence 
of salts of iron in solution is necessary for their vigorous growth, 
and they have the curious power of withdrawing this iron from 
the water and depositing it in the form of ferric oxide as a sheath 
or tube around the filament. The color of this sheath, which at 
first is hardly noticeable, passes through this accumulation of iron 
from pale yellow to deep brown, and there is at the same time a 
gradual thickening of the wall. The thick and hard sheath then 
seems no longer suited to the activities of the plant, and is 
abandoned by the cells, which, as they work out from it, cause 
it to take on an increase of length or a structure which suggests 
branching. 

Crenothrix has at several times been the cause of serious trouble 
in the water-supplies of European cities, notably at Berlin in 1878, 
and at Rotterdam in 1887. Its occurrence in this country is well 
established, and it is known to be common in Massachusetts. It 
may be removed and kept out of a water by thorough filtration, 
but may grow rapidly in an imperfectly filtered effluent. Light 
is not necessary for its growth, and in fact it thrives best in dark 
reservoirs or galleries and in systems of pipe. 

All waters consume small quantities of bleaching-powder, the 
amount in each case depending upon that of the organic matter 
present in the water. Except in rare cases, the loss of bleach thus 



WATER. 333 

occasioned is inappreciable, as appears from our results given 
below: — 

Volatile and inorganic Bleaching-powder (36 per 

matter in water. cent.) consumed. 

0.93 grains per gallon. 1.77 grains per gallon. 

0.35 1.16 

1.167 3.87 

The mineral constituents of a water affect its value for paper- 
making mainly as they bear upon the suitability of the water for 
boiler purposes. As already pointed out, a soft water is desirable 
for some of the operations of the mill, but its use in a boiler is 
almost essential if trouble from scale is to be avoided. Accord- 
ing to Haswell, a coating of scale one-sixteenth of an inch in 
thickness causes a loss of fuel equal to 14.7 per cent., while we 
have seen samples of scale an inch and a quarter thick. When 
any considerable thickness of scale is present, there is much danger 
of overheating the boiler locally. This is often followed by blis- 
tering or cracking of the plates or collapsing of the tubes, and 
may even cause explosion, due to the breaking of the scale and 
the sudden contact of the water with the overheated plate below. 

Carbonate of lime is the most frequent cause of boiler scale. 
It is normally very slightly soluble in water; but if the water 
contains dissolved carbonic acid, the lime may be brought into 
solution as bicarbonate in very considerable amount. The bi- 
carbonate is the cause of what is called temporary hardness, for 
upon boiling it is decomposed, with precipitation of the carbonate. 
According to Couste, this precipitation is complete at 200° F., or 
under the conditions which obtain in most boilers. Carbonate of 
magnesia, which is similarly soluble in the presence of dissolved 
carbonic acid,, and similarly precipitated on boiling, is also likely 
to form scale. Chloride of magnesia, although extremely soluble 
in water, is nevertheless objectionable, because at high pressures 
it is decomposed, with liberation of hydrochloric acid and forma- 
tion of hydrate of magnesia, the latter acting as a sort of cement 
in binding together other scale-forming materials. The precipi- 
tated carbonate of magnesia undergoes a like decomposition, 
carbonic acid being set free. 

The general character of a carbonate scale appears from the 
following analysis, but the proportions show considerable varia- 
tion in different samples. 



334 THE CHEMISTRY OF PAPER-MAKING. 

Analysis of a Carbonate Scale. 

(Silvester.) 

Per cent. 

Carbonate of lime 75.85 

Sulphate of lime 3.68 

Hydrate of magnesia , . 2.56 

Chloride of sodium 0.45 

Silica 7.66 

Oxides of iron and alumina 2.96 

Organic matter . . . . 3.64 

Moisture 3.20 

100.00 

Sulphate of lime, although rather soluble in water, has its point 
of greatest solubility at 95° F., and from a solution saturated at 
this temperature, the salt is therefore gradually thrown out as the 
temperature rises. Moreover, the hydrate d sulphate, CaS0 4 2 H 2 0, 
begins to lose its water of crystallization at about 260° F., and is 
converted into the anhydrous sulphate, CaS0 4 , which is far more 
insoluble. Both these actions combine to produce a hard scale as 
the sulphate accumulates in the boiler, and the usual methods of 
softening water are of comparatively little value when sulphate 
of lime is present. 

Much silica is troublesome in a water used for boiler purposes, 
as, when deposited, it serves as a binding material and causes the 
production of a very hard scale. 

Acid waters are rarely met with in this country, where there ^s 
comparatively little contamination of streams by manufacturing 
waste ; but in sulphite mills there is danger, if for any reason 
check-valves do not work properly, that some of the liquor from 
the digesters may find its way into the generating boilers and 
cause corrosion, which is more to be dreaded than scale. Cylinder 
oils not infrequently contain free fatty acids, and when these are 
present, they pass with the feed water back into the boiler and 
corrode the metal. Very alkaline waters also are apt to attack 
the boiler fittings and cause leakage. 

A 100-horse-power boiler evaporates 30,000 lbs. of water in 10 
hours, or 900 tons in 25 days of continuous working. Since the 
mineral matters remain behind in the boiler as the evaporation 
of the water proceeds, it becomes obvious that apparently insig- 



WATER. 335 

nificant amounts of mineral impurity may, in this process of 
concentration, accumulate to such an extent as to cause serious 
inconvenience from mud and scale. A deposit of scale -^ of an 
inch in thickness has already been said to cause a loss of fuel of 
14.7 per cent., while if the scale is ^-inch thick, the loss is said to 
amount to 38 per cent. A great many materials have been pro- 
posed for use in boilers as preventives of scale, but most of them 
are of doubtful value. Organic substances containing tannic acid, 
as, for instance, oak or hemlock bark, are sometimes used, their 
value depending on the tannic acid. Other materials, which either 
contain acetic acid, or which are of such a nature that the acid 
may be developed from them under the heat and pressure of the 
boiler, have also been used with some success, but are objectionable, 
from the danger that the acid due to them may corrode the boiler. 
Crude or refined petroleum has been recommended for use with 
waters containing large amounts of sulphate of lime. The refined 
oil is preferable, as the residuum from the crude oil is apt to ' cake 
on the plates and bind the scale more firmly. Abroad, sulphate 
waters are purified by the addition of carefully regulated amounts 
of either caustic soda or soda-ash, or, more rarely, barium chloride. 
Both the caustic soda and soda-ash result in precipitation of car- 
bonate of lime, but the soda-ash is to be preferred. The barium 
chloride forms the very soluble chloride of calcium and the insolu- 
ble sulphate of barium. If the alkalis are used, much care is 
necessary to secure the proper amount, as an excess causes 
foaming. 

The method for softening waters which is most generally used 
is that which is especially applicable to waters containing lime or 
magnesia as bicarbonates, and which is due to Dr. Clark. The 
Clark process depends upon the fact that when lime is added to 
such waters the extra equivalent of carbonic acid is neutralized, 
with the result that the lime originally present in the water, 
together with the added lime, is thrown down as the insoluble 
neutral carbonate, while the bicarbonate of magnesia is at the 
same time decomposed, with precipitation of the magnesia as 
hydroxide. Various modifications of the Clark process have 
appeared, which base their claims to improvement upon changes 
in the apparatus employed. The process is perhaps now most 
commonly worked under the form known as the Porter-Clark 
process, the apparatus for which is shown in Fig. 72. 



336 



THE CHEMISTRY OF PAPER-MAKING. 



The tank shown at the left of the figure is fitted with a mechan- 
ical agitator, and is used for preparing the lime-water by admix- 
ture of water and milk of lime, the latter being introduced through 
the funnel. The lime-water in a carefully regulated stream then 
flows over into the second tank, where it meets the water to be 
purified. The outflow from this tank is so controlled as to allow 
sufficient time for the completion of the desired reaction, and is 




Fig. 72. — The Porter-Clark Process. 



finally sent through a filter-pump, which retains the precipitated 
material and discharges the softened and clarified water. 

Filtration. — The purification of water by filtration is a much 
more complex series of actions than a mere mechanical straining, 
though this is the most noticeable, and from our present point of 
view the most important, office of filtration. In the slow passage 
of water through a filtering medium, the principle of subsidence 
comes in play to hold back particles so fine that they would other- 
wise pass the interstices of the filter, and the water is at the same 
time subjected to influences which set up changes of both the 
chemical and biological order. 



WATER. 337 

The primary action of a filter is, then, a straining one, to remove 
the coarser particles of suspended mineral and vegetable matter in 
the water. It is obvious, in addition, that if the water were stand- 
ing in a tank, it would gradually clear itself of these impurities by 
the settling due to gravity. The length of time thus required 
would depend, other things being equal, upon the depth of water 
in the tank. If now the tank were divided by a midway horizontal 
partition, or false bottom, the average distance which each sus- 
pended particle must fall in order to find a resting-place is halved, 
and the time needed for the action similarly lessened. Within a 
filtering medium the number of shelves or surfaces upon which 
the finest particles may find lodgment as they settle is immensely 
great, and it is in large part to this fact that the efficiency of the 
medium is due. 

The action of porous earth, when the passage of water through 
it is intermittent, is an oxidizing one of high order, from the fact 
that the water and the gas are brought so intimately into contact. 
In the natural filtration to which surface waters are subjected 
during their transformation into ground waters, this action may 
proceed so far under favorable conditions as to completely oxidize 
all the organic matter originally present. In this way not only is 
the suspended organic matter removed, together with the silt, by 
the process of straining, but the dissolved organic matter to which 
much of the color may have been due is consumed by oxidation, 
leaving the water, as in case of all perfectly filtered waters, entirely 
clear and colorless. The same process goes on to a considerable 
extent in artificial filtration, where the flow of water is intermittent 
and properly controlled. In continuous filtration there is little or 
no oxidation of organic matter, and other means are used to secure 
its removal. 

The filtration of water has been mainly studied scientifically 
with reference to its sanitary aspect, and from this point of view 
the removal of bacteria and other organisms is the matter of first 
importance. It has been found that a layer of fine sand one inch 
in depth is sufficient to remove all algae and animals from a water 
as rich in organisms as the Cochituate water of Boston. 

In Europe open filter-beds are very generally used for the puri- 
fication of water by filtration, and where the purification is for 
municipal purposes, the beds are sometimes of enormous extent. 
The filter-beds of the various London water companies cover an 



338 THE CHEMISTRY OF PAPER-MAKING. 

area of more than 100 acres. The continental cities have exten- 
sive and similar plants. The beds are built up of stones which 
decrease in size toward the top of the bed, and which are covered 
with a layer of fine sand, generally two inches in thickness. The 
average capacity of such filter beds is found to be 1,000,000 gallons 
per acre per twenty-four hours. Under these conditions there is 
formed upon the surface of the filter-bed a growth of bacteria 
which is called the bacteria jelly, and which prevents almost en- 
tirely the passage of bacteria through the filter, while of course at 
the same time holding back the suspended impurities in the water. 
The water of the Spree contains, for instance, under normal condi- 
tions, about 100,000 bacteria per cubic centimetre, while after pass- 
ing through the filter-bed it has only 30-40 per cubic centimetre 
when the rate of flow is 1,000,000 gallons, and only 4-5 when the 
rate falls to 300,000 gallons per day. 

The economic and climatic conditions which prevail in this 
country almost entirely preclude the operation of such extensive 
plants of relatively small capacity, so that most municipalities 
and factories requiring filtered water make use of some form of 
mechanical filter. These may be grouped under two systems, — 
gravity filters and pressure filters, — and we shall limit ourselves 
to the description of representative types of each system. 

The efficiency of filters working under either of these systems 
is increased, and a partial chemical, as well as a complete mechani- 
cal, purification of the water effected by the introduction with the 
water of small quantities of alum or other coagulant. A crude 
sulphate of alumina is generally employed, and seems to give better 
results than crystallized alum. The alumina precipitated by the 
action of the alkaline water not only gathers the finely suspended 
material into flocks of appreciable size, but also removes the dis- 
solved organic coloring-matter, and forms a film over the surface 
of the filter, which acts, as does the bacteria jelly before mentioned, 
in holding back minute organisms. The quantity of alum thus 
used varies from \- grain to 2 or 3 grains per gallon, the usual 
maximum being 2 grains. If very large amounts of loam are 
present in the water, small quantities of lime may sometimes be 
used first, and then alum. 

The form of gravity filter which has been most generally intro- 
troduced is the Warren filter, shown in Figs. 73 and 74. A 
Warren filter-plant usually consists of a settling-basin, one or 



WATER. 



339 



more filters, and a weir for controlling the head, together with 
the necessary pipe connections. Each filter contains a bed of fine, 
sharp sand, (7, two feet in depth, supported by a perforated copper 
bottom, B, and for cleaning this bed an agitator, D, is provided. 
This consists of a heavy rake containing 13 teeth 25 inches long, 
rotated by a system of gearing, JT, and capable of being driven 
into the bed by means of suitable screw mechanism, LM, whereby 
the entire bed is thoroughly scoured. 

The process of filtration is as follows : The water enters the 
settling-basin through a valve operated by a float, by which a 




Eig. 73. — The Warren - Filter. — In operation'. 



constant level is maintained in the entire filter-system. The 
water entering through this valve passes through an 8-bladed 
propeller of brass, from 10 to 16 inches in diameter, so arranged 
as to revolve freely with the passage of the water. This, by means 
of two small bevel gears and an upright shaft, operates an alum 
pump, consisting of six hollow arms radiating from a chambered 
hub and bent in the direction of rotation. This pump revolves in 
a small tank containing a dilute standard solution of. sulphate of 
alumina, or other coagulant, and by its revolution each arm takes 



340 



THE CHEMISTBY OF PAPER-MAKING. 



up its modicum of alum water, passes it into the hub and to the 
deflector, which sends it down to the incoming water. 

When the bed of a filter becomes clogged, and it seems best to 
clean it, the inlet and outlet valves EF are closed, and the wash- 
out Gr opened, allowing the contents of the tanks to escape to 
the sewer. The agitator D is then set in motion by means of the 
friction clutch with which it is equipped ; and as the teeth on the 
rake begin to plough up the surface of the bed, a slight amount 
of filtered water is allowed to flow back up through the bed, in 




Fig. 74. — The Warren Filter. — During Washing. 



order to rinse off the dirt loosened by the scouring action of the 
rake. This is kept up until the rake penetrates to the bottom of 
the bed, and thoroughly agitates every particle of material therein. 
As soon as the water flowing to the sewer appears to be clear, the 
motion of the rake is reversed, and it is slowly withdrawn from 
the bed. When the teeth are raised above the bed, the waste pipe 
is closed, the inlet valve E opened, and the filter-tank allowed to 
fill. After waiting a few minutes for the tank to resume its nor- 
mal condition, the outlet valve F is slowly opened, and filtration 
is resumed. 



WATER. 341 

The incoming water, having received its proportionate amount 
of coagulant, is then allowed to remain in the settling-basin from 
thirty to forty minutes, to enable the chemical reaction between 
the coagulant and the bases in the water to take place, and to 
permit of the heavier sediment, together with a portion of the 
coagulated matter, to settle by subsidence to the bottom of the 
tank, where it can be drawn off at intervals into the sewer. 

The partially purified water then passes on through suitable 
piping and valves to the filter, and, filling the tank, passes down 
through the fine sand bed, leaving all the coagulated matter upon 
it. The filtered water makes its exit through the main I. 

The main, collecting the filtered water from the various filters, 
passes along between them to the head-box, or weir, over which 
the water is compelled to pass, and which controls the operation 
of the filters. The top of this weir is 20 inches below the water 
level maintained in the filter-system, and this head of 20 inches 
(equivalent to a pressure of three-fourths of a pound to a square 
inch) is the extreme pressure that can be brought to bear upon 
the filters, and it is claimed that they can at no time be pushed 
beyond the rate which experience has shown to yield the best 
results. 

Two sizes of the Warren filter are built, both being 8 feet high. 
The smaller filter is 8 feet 8 inches in diameter, and has a capacity 
under alum of 200,000-250,000 gallons per twenty-four hours on 
a net area of 56 square feet. The large size is 10 feet 6 inches in 
diameter, its net area being 84 square feet, and its capacity 300,000- 
375,000 gallons. About 5 horse-power is required for each agita- 
tor; but as only one filter is washed at a time, the quantity of 
power required is irrespective of the size of the plant. The filters 
are usually washed every twelve hours. 

The especial points of merit claimed for this system are, first, 
its cheapness, and, second, the thorough and rapid cleansing of the 
bed by the attrition of its particles set up by the mechanical stir- 
ring and scraping action of the rake. 

The forms of pressure filter shown in Figs. 75 and 76, and built 
by the New York Filter Company, embody the best features of the 
numerous systems which, after being developed on somewhat 
divergent lines, have now been brought under the single control 
of this company. The filter shown in Fig. 75 consists of a cylin- 
drical steel shell built to withstand any desired pressure. The 



342 



THE CHEMISTRY OF PAPER-MAKING. 



water is introduced along a conduit running the entire length of 
the filter just beneath the crown. It filters through 4 feet of coke 
and sand, and passes out by the cone valves shown at the bottom. 
These valves are imbedded permanently in a cement floor and 
flush with it. They are filled with screened quartz gravel to 
prevent the passage of the filtering medium into the mains. 

The method of cleansing the filter adopted by this company is 
that known as sectional washing, by which the entire force of the 
reversed current used in washing is directed against one-third* of 
the bed only for about five minutes ; it is then shut off, and the 
central third of the bed is scoured in the same manner ; last, the 
remaining third is washed. No partitions are necessary to divide 
the bed, as the current is forced up nearly in a straight line. By 




Fig. 75. — Sectional Washing Pressure Filter. 
Filter Company. 



New York 



thus concentrating the force of the upward current against a small 
portion of the bed, thorough attrition and scouring of the particles 
composing the bed is accomplished, while the upward current 
carries away the separated impurities. The capacity of such a 
filter 8 feet in diameter and 20 feet long is about 500,000 gallons 
per twenty-four hours; or, in other words, two such filters have 
the capacity of a European filter-bed one acre in extent, when the 
latter is worked at the rate recommended by the Berlin authorities; 
Fig. 76 shows a vertical washing-filter of essentially the same 
type. These are built in sizes ranging from 12 inches to 10 feet 
in diameter, and have a maximum capacity per twenty-four hours 
from about 4000 to 360,000 o-allons. The filter consists of a verti- 
cal steel shell, the cone valves at the bottom being set on rubble 
grouting and imbedded in cement. The space above is about two- 



WATER. 



343 



thirds filled with fine quartz sand and coke. The water to be 
purified is admitted under pressure to the filter at A, which 
delivers the water at the crown of the filter. It then passes down 
through the bed and out through the cone valves to the outlet B, 
leading to the service pipe. As often as may be necessary, usually 
once a day, the water is shut off from the inlet and allowed to 
enter the filter in the upward direction through the lower valves. 
These are so arranged as to admit the water to the cones under- 




Fig. 76. — Sectional Washing Pressure Filter. — New York 
Filter Company. 



lying one-third of the bed at a time, and the waste water, carrying 
with it the impurities, passes to the sewer through K. 

A minute quantity of alum solution is injected into the water 
passing to these filters, as in case of practically all systems of fil- 
tration in use in this country. In the present instance a special 
alum pump is employed which delivers a positive quantity of the 
solution, which is carefully regulated to suit the requirements of 
the water. 

A novel form of plant is the Dervaux automatic water-purify- 
ing apparatus, shown in Fig. 77, for which we are indebted to the 
Papier-Zeitung. The action of the apparatus is a double one, cor- 



344 



THE CREMISTBY OF PAPER-MAKING. 



WaBseiv 

zufluss ' 




mL, „-—. — ^ __ ~-*^ 

Fig. 77. — Dervaux Water-Purifier. 

EXPLANATION OF TEEMS. 

Wasserzufluss = "Water inlet. Kalksattiger = Lime-saturator. 

Gereinigtes Wasser = Purified water. Soda = Carbonate of soda. 

Kalkeinschuttung = Inlet for lime. Schlammabfluss = Outlet for mechanical impurities. 



WATER. 345 

responding to the double nature of the impurities present in the 
water ; that is, it not only acts to precipitate the dissolved impuri- 
ties, but also to separate such impurities as are in suspension. 
These last are caught and held in the tower-shaped holder D. 
The water enters from above, down through F, and is made to 
rise through a series of funnels or inclined funnel-shaped walls. 
On these walls the coarsest particles are caught, and from them 
they flow down to the bottom of the tower, where they collect 
together; the water then passes upwards through the filters _F, 
which are made of wood shavings, and flows off, freed from its 
mechanical impurities, through the opening T. In the mean time, 
by the addition of lime and soda, the water has been chemically 
purified in the following way : — 

The water first flows in the reservoir C, through the pipe H. 
In there is a float for regulating the flow of water. By the 
arrangement of the apparatus, a part of the water goes into F, 
through the pipe P, while the rest passes through the valve V 
into the lime-saturator S; S is filled with lime ; the water first 
meets the lime at the bottom of the saturator and passes up 
through it; the conical shape of S causes the rise to be slower 
and slower as the water nears the top, so that the milk of lime 
at first formed has plenty of time to clarify itself. The lime-water 
usually contains some carbonate of lime in suspension ; and as this 
is worthless for purpose of purification, it is eliminated by causing 
the water to flow over into the cone K, which is closed at the 
bottom. In this cone the carbonate settles out, and may be drawn 
off through G-. 

The clear, saturated lime-water, containing 1.3 grammes of lime 
to the litre, runs then directly into the mixing-tube F. A solution 
of soda-ash is made up of a strength always exactly the same, by 
taking a known weight of ash, which is placed in the cage Z, after 
which the tank B is filled to a definite mark with water. This 
solution slowly passes through the tube, provided with strainers : 
a float in the tube keeps the water in 5ata constant level. The 
siphon N, one end of which dips to the bottom of B, allows the 
alkaline solution to flow into B. The regulation of the flow in E 
is done as follows : — 

The siphon iTis joined by a chain, Q, to the float in C. In case 
the flow of water through H to C is cut off, the float sinks, raising 
iVand thus stopping the flow of the solution. At the same time 



346 THE CHEMISTRY OF PAPER-MAKING. 

the level in C sinks so low that the flow of water through P and 
V ceases ; as soon as the flow of water through H recommences, 
the apparatus is again set in operation automatically. 

The whole apparatus comes to a standstill as soon as the draw- 
ing off of the pure water at T stops ; this is effected by a float in 
D not shown. 

The chemical reaction going on in the apparatus was roughly 
this : — 

The addition of the lime softens the water by precipitating any 
bicarbonate which may be present, and the excess of lime is 
thrown down by the carbonate of soda. This, by its precipitation, 
coagulates and throws out much of the finely divided organic 
impurity. The apparatus may be easily modified to work with 
alum where desirable. The water from T is said to. be sufficiently 
free from chemical and mechanical impurity for all practical pur- 
poses. The yield of the apparatus varies, according to its size, 
from *- to 50 c. m. per hour. Larger sizes are also made and 
we are informed that 109 of these plants are in use in Europe at 
the present time. 



In taking a sample of water for analysis, especially if any opin- 
ion as to its healthfulness is desired, much care must be observed 
to avoid contamination of the sample. A perfectly clean glass- 
stoppered bottle of about 1 gallon capacity should be used. The 
State Board of Health of Massachusetts has issued the following 

Instructions for collecting Samples of Water for 

Analysis. 

1. From a Water Tap. — The water should run freely from 
the tap for a few minutes before it is collected. The bottle is 
then to be placed directly under the tap, and rinsed out with 
water three times, pouring out the water completely each time. 
It is then again to be placed under the tap, filled to overflowing, 
and a small quantity poured out, so that there shall be left an air- 
space under the stopper of about an inch. The stopper must be 
rinsed off with flowing water and inserted into the bottle while 
still wet, and secured by tying over it a clean piece of cotton 
cloth. The ends of the string must be sealed on the top of the 
stopper. Under no circumstances must the inside of the neck of 



WATER. 347 

the bottle or the stem of the stopper be touched by the hand or 
wiped with a cloth. 

2. From a Stream, Pond, or Reservoir. — The bottle and stop- 
per should be rinsed with the water, if this can be done without 
stirring up the sediment on the bottom. The bottle, with the 
stopper in place, should then be entirely submerged in the water, 
and the stopper taken out at a distance of 12 inches or more below 
the surface. When the bottle is full, the stopper is replaced 
below the surface if possible, and finally secured as above. It 
will be found convenient, in taking samples in this way, to have 
the bottle weighted, so that it will sink below the surface. It is 
important that the sample should be obtained free from the sedi- 
ment on the bottom of a stream and from the scum on the sur- 
face. If a stream should not be deep enough to admit of this 
method of taking a sample, the water must be dipped off with an 
absolutely clean vessel, and poured into the bottle after it has 
been rinsed. 

The sample of water should be collected immediately before 
shipping by express, so that as little time as possible shall inter- 
vene between the collection of the sample and its examination. 

In case there are any abnormal or unusual conditions existing 
in the source of the water, mention the facts : as, for instance, if 
the streams or ponds are swollen by recent heavy rains; or are 
unusually low in consequence of prolonged drought ; or if there 
is a great deal of vegetable growth in or on the surface of the 
water. 



348 



THE CHEMISTRY OF PAPER-MAKING. 



CHAPTER VIII. 



CHEMICAL ANALYSIS. 



Under this head we shall make no attempt to map out elaborate 
methods for the complete analysis of the different substances 
named, except in special instances, as such a course would clearly 
be beyond the scope of the present work. It would also, in many 
cases, call for more or less complicated and expensive apparatus, 
as well as a skill in chemical manipulation, which one could only 
expect to find in the well-equipped laboratory of the professional 
chemist. 

There are, however, very many tests of value which may be 
readily applied by one not specially skilled in analytical methods, 
and which require for their application but a limited amount of 
apparatus. Such tests, if carefully carried out, will very often 
serve the manufacturer's purpose quite as well as a more extended 
analysis, and at other times may indicate the desirability of such 
analyses. 

Our purpose here, then, is to bring together certain easily 
applied and reliable tests for ascertaining the purity or " strength " 

of the chemicals more or less 
directly concerned in the art 
of paper-making. In some 
few instances, for example, 
alums and sulphite liquors, 
we have thought it well to 
lay down a plan for the com- 
plete analysis of the sub- 
stance. 

The apparatus required for 
preparing the necessary solu- 

Fig. 78. -Analytical Balance. tions ' and making the tests 

named, consists of : — 
1. A balance (Fig. 78), sensitive to ^-milligramme, and capable 
of carrying a maximum load of 200 grammes in each pan. The 




CHEMICAL ANALYSIS. 



349 




Fig. 79. — Measuring Flasks. 



balance should be enclosed in a glass case to protect it from dust 
and acid vapors, as well as from drafts of air while weighing. 

2. A set of weights ranging from a 100-gramme piece to a 
1-milligramme piece. These should be kept in a box with a tight- 
fitting cover for protection from 
dust and dampness. 

3. Measuring-flasks (Fig. 79), 
holding respectively 1000 c.c, 
500 c.c, 250 c.c, 100 c.c, and 
50 c.c, when filled to the mark 
engraved on the neck. 

4. Two burettes, which are 
simply straight tubes of glass 
graduated into cubic centime- 
tres and tenths of cubic centi- 
metres. The most convenient 
size holds 50 c.c One of these 

(Fig. 80), is narrowed at its lower extremity, and is to be fitted 
with a piece of rubber tubing about 2 inches long, one end of 
which is slipped over the narrowed end of the burette, while the 
lower end of the tubing carries a short piece of glass tube which 

has been drawn out to a fine point. 
By means of a spring-clip, or pinch- 
cock, which pinches the rubber just 
above the glass tip, any desired quan- 
tity of the liquid in the tube may be 
run out. 

The other burette should be provided 
with a glass cock, and is used to contain 
such liquids as would act upon rubber 
and be injuriously affected by it, as 
caustic soda or iodine solutions. 

The manner of using these instru- 
ments will be shown farther on. 

5. A burette stand like that shown 
in Fig. 80, or some arrangement for 
holding burettes firmly in a perpen- 
dicular position, and which will at the 
same time permit their ready removal for cleaning and filling. 
A simple screw clamp of wood or iron lined with cork fixed firmly 




350 



TEE CEEMISTEY OF PAPER-MAKING. 



to an upright, or to the wall of the room, answers the purpose 
well. 

6. Plain flasks, ungraduated, of different sizes, ranging in capac- 
ity, perhaps, from 2 or 4 oz. to 32 oz. 




Fig. 81. 

7. Beaker glasses (Fig. 81) of different sizes. These are by 
preference of the low wide form with lip for convenience in pour- 
ing. They are known as Griffin's beakers. They may best be 
obtained in nests as shown in the figure. Sizes holding from 4 oz. 
to 20 oz. are the most convenient. 

8. Convex glasses knoAvn as clock glasses. These are to serve 






Fig. 82. 



Fig. 83. 



Fig. 84. 



as covers for the beakers when required, and the sizes should 
be chosen with that end in view. They serve also for use in 
weighing such substances as iodine, which would injure the bal- 
ance pan if placed directly upon it. 

9. A number of pieces of solid glass 
rod 6 to 8 inches in length, with the 
ends rounded by fusing in a flame. 
These are for use as stirrers. 

10. Crucibles, with covers, of Royal 
Berlin porcelain, 1-*- inch diameter 
(Fig. 82). Also 2 or 3 each of dif- 
ferent sizes of evaporating-dishes 

(Fig. 83) of the same ware. Two or three casseroles (Fig. 
84) will also be found convenient 




Fig. 85. 



CHEMICAL ANALYSIS. 



351 




11. A copper water-bath (Fig. 85), 6 inches in diameter, for use 
with the dishes last named. 

12. A ring stand (Fig. 86) to support dishes and crucibles while 
being heated. An iron tripod is also needed to 
support the water-bath. 

13. Two or three lamps for gas or alcohol, 
as the case may be. Where gas cannot be had, 
the Kellogg gasoline lamp for laboratory use 
gives excellent satisfaction, and with ordinary 
care is free from danger. Where alcohol is 
employed for heating, a Russian blast lamp, so- 
called, is a convenience and often almost a ne- 
cessity. 

14. Glass funnels of 60° angle. 2, 4, and 
6-inch diameters are convenient sizes. 

15. A 4-inch porcelain mortar for grind- 
ing samples, etc. 

16. An evaporating-dish of platinum hold- 
ing 50 to 100 c.c, and a crucible of the same 
metal of 15 to 20 c.c, capacity with a cover ; 
also a triangle of stout platinum wire for 
supporting crucibles over the flame. 

17. A set of reagent bottles, and several 
green glass bottles, holding 1- gallon each, 
with glass stoppers, for holding standard 
solutions. 

18. A dozen or two of 6-inch test-tubes, 
which for convenience in shaking should be not too wide to be 
easily covered by the thumb, some 
tubing of soft glass of about |-inch 
bore, with a few feet of rubber tub- 
ing to match ; a desiccator (Fig. 87) 
and a pair of crucible tongs (Fig. 
88) make up the list of apparatus. 
The manner in which these various 
pieces of apparatus are to be used will be explained as they 




Fig. 87. 




are called for in the tests which follow. 



352 THE CHEMISTRY OF PAPER-MAKING. 



NORMAL SOLUTIONS. 

In the testing of certain substances, notably acids and alkalies, 
it is often most convenient to calculate their strength by ascer- 
taining the quantity of a solution, the strength of which is known 
beforehand, it will take to neutralize or balance a definite quantity 
of the solution to be tested. 

In such instances the test solution is called a standard solution, 
and is always either made and used of an exact and definite 
strength known as normal strength, or the actual volume em- 
ployed of a strength other than normal is reduced in the calcu- 
lation to the equivalent volume of normal strength by the use of 
a previously ascertained factor. Normal solutions then are always 
made on the simple and definite plan of having each 1000 c.c. of 
solution contain the number of grammes of pure substance repre- 
sented by the molecular weight of that substance if its valency is 
one, one-half the molecular weight if the valency of the substance 
is two, one-third if the valency is three, etc. Thus, for example, 
to make a normal solution of sodium hydrate, NaHO, the val- 
ency of which is one, and its molecular weight 40 (Na23 + H 1 + 
O 16 = 40), 40 grammes of NaHO must be dissolved to make 1000 c.c. 
of solution. 

To make normal sulphuric acid we dilute one-half the molec- 
ular weight in grammes to 1000 c.c, since sulphuric acid is a 
bivalent acid, or in figures H 2 S0 4 = molecular weight 98, -r-2 = 49 
grammes to the litre. The initial N is commonly used as an ab- 
breviation for normal. When made upon this plan it will always 
be found that equal quantities by volume of any two normal solu- 
tions whose chemical properties are opposite will e'xactly balance or 
neutralize each other. For example, 100 c.c. N of soda solution 
will exactly neutralize 100 c.c. N of sulphuric, or a like amount 
of any other normal acid solution. Again, 50 c.c. of normal arsenic 
solution will exactly neutralize 50 c.c. of normal iodine. In prac- 
tice it is difficult in most cases to make a strictly normal solution 
on account of slight impurities often present in so-called chemically 
pure chemicals, and the difficulty of accurately weighing many 
substances. It is usually much more convenient to weigh approxi- 
mately the required number of grammes per litre of the substance 
in hand, and after the solution has been made up to volume, to 



ACTUAL ANALYSIS. 353 



accurately determine by appropriate means the actual amount of 
the given substance it contains per cubic centimetre, and this done 
it is easy to find a factor by means of which to reduce any number 
of c.c. of this solution to equivalent c.c. of normal solution. For 
example, we have made up a solution of caustic soda (NaHO) 
and find that it contains 0.0398 grammes of NaHO per cubic centi- 
metre, instead of 0.0400 grammes, which a strictly normal solution 
would contain. 

Then to find the factor for reducing this solution the proportion 
should be, as 0.04 (normal solution) is to 0.0398 (our solution), so 
is 1 c.c. to x (0.04: 0.0398 = 1 :x= 0.995), and we find the factor 
to be 0.995. In other words, 100 c.c. of our solution equals 99| 
c.c. of normal solution. 

The method of analysis by the use of normal solutions is called 
volumetric analysis, in distinction from gravimetric analysis, in 
which latter the substance to be estimated is converted into some 
definite compound insoluble in the given menstruum, and which is 
then separated, dried, and weighed, when, from the weight of the 
compound, that of the substance wanted is calculated. In gravi- 
metric analysis, the exact strength of the reagent solutions 
employed is not necessarily known. 

In every method of chemical analysis, cleanliness of apparatus 
employed, and the utmost care to guard against loss, and to secure 
accuracy in weighing and measuring, are essential in order to 
secure reliable results. 



ACTUAL ANALYSIS. 

ACIDS. t 

Unite with alkalis and metallic salts. — Solutions in water turn litmus red. 

Sulphuric Acid (Oil of Vitriol). 

Symbol, H 2 S0 4 . — Valency, II. — Molecular weight, 98. 

For specific gravity of solutions of H 2 S0 4 , and percentage of actual H,,S0 4 con- 
tained, see Appendix. 

The presence of sulphuric acid, either free or in combination, 
may be recognized in solution by means of barium chloride solu- 
tion, which forms, with sulphuric acid, or soluble sulphates, a 
heavy, white, very finely divided compound of barium sulphate 



354 THE CHEMISTRY OF PAPER-MAKING. 

(BaS0 4 ). This compound is insoluble in water, and very nearly 
so in dilute hydrochloric acid, even on boiling. It is soluble only 
very sparingly in strong boiling hydrochloric acid. 

Free sulphuric acid in a solution not containing other free acids 
may be estimated volumetrically by means of standard soda solu- 
tion as follows : — 

Forty-nine grammes are weighed in a beaker, and made to 1000 
c.c. with water, and the solution well shaken up. The beaker should 
be rinsed several times with water, and the rinsings poured into 
the 1000 c.c. flask, which is then filled to the mark, and shaken. 
100 c.c. of this solution are then measured out in the 100 c.c. 
measuring flask, and transferred to a beaker, or porcelain dish, 
and the small flask rinsed several times with water, the rinsings 
being added to the liquid in the beaker. A few drops of litmus 
solution are added, and the whole warmed over the lamp. While 
the solution is warming, a burette with rubber tip should be filled 
just to the zero mark with standard soda solution. When the acid 
solution in the beaker has come to a boiling heat, the soda solution 
from the burette is run in, a little at a time, stirring the contents 
of the glass after each addition until the color of the solution has 
just changed from the red, which it has previously exhibited, to a 
purple tint. The number of cubic centimetres, and tenths of cubic 
centimetres, of soda solution used is now read off from the burette, 
and converted, by means of the appropriate factor, into normal 
cubic centimetres. The number of normal cubic centimetres 
employed represents directly the percentage of H 2 S0 4 in the 
original solution, a portion of which was weighed out for the test. 
If the solution to be tested is weak, it is convenient to weigh 
twice, or three times, the amount named above (49 grammes), and 
dilute it to 1000 c.c, taking 100 c.c. of this solution, as before, for 
the actual test. In such case, of course, the number of normal 
cubic centimetres employed must be divided by 2, or 3, as the case 
may be, to give the per cent. 

When free acids, other than sulphuric acid, are present with 
the latter in solution, the amount of this acid cannot be estimated 
by means of standard soda, but it must be separated and weighed, 
as in the estimation of sulphuric acid in Sulphates below, which 
see. 

The impurities to be looked for in commercial oil of vitriol are 
lead, arsenic, nitric and nitrous acids, and occasionally ammonia. 



ACTUAL ANALYSIS. 355 



Hydrochloric Acid {Muriatic Acid). 

Symbol, HC1. — Valency I. — Molecular weight, 36.5. 

For specific gravity of solutions and percentage of HCi contained, see Appendix. 

Hydrochloric acid may be recognized in solution, either when 
free or combined with bases, by means of solution of silver nitrate. 
When solution of silver nitrate is added to a solution containing 
HCI, or chlorides previously acidified by the addition of a, few 
drops only of nitric acid, a white, curdy precipitate of silver chloride 
is formed which is insoluble in dilute nitric acid, either cold or hot. 
It is slightly soluble in strong nitric acid, and readily dissolved by 
ammonia water. The white chloride of silver precipitate, when 
exposed to strong daylight, rapidly turns purple, and after a little 
time becomes nearly black. If much organic matter is present in 
the solution tested, it often interferes with the above reaction, and 
may obscure it entirely by the formation of a black precipitate. 
In this case the solution must be evaporated to dryness, and gently 
ignited to carbonize the organic matter. It is then treated with 
water, and the resulting solution filtered and tested with silver 
nitrate. 

Free hydrochloric acid in solution, other free acids not being 
present, may be estimated by means of standard soda solution. 
For this purpose 36.5 grammes of the solution are weighed out 
and made to 1000 c.c, as in testing Sulphuric Acid above, which 
see. 100 c.c. of the prepared solution are transferred to a beaker, 
or porcelain dish, as above, colored with litmus solution and 
standard soda solution run in from the burette, until nearly all the 
acid is neutralized. The solution is then heated to boiling, and 
the soda solution dropped in until the purple color appears. The 
number of cubic centimetres of soda solution used represents 
directly, after reduction to normal cubic centimetres by means of 
the appropriate factor, the percentage of HCI in the original solu- 
tion weighed out. 

To estimate HCI in solution with other free acids it must be 
separated and weighed as silver chloride, or, after neutralization, 
titrated with standard silver nitrate solution. For details of both 
these methods, see under Chlorides, below. 

The impurities to be looked for in commercial muriatic acid are, 
sulphuric acid (sulphurous acid occasionally), iron, and other 
metals, and frequently arsenic in small amount. 



356 THE CHEMISTRY OF PAPER-MAKING. 

Nitric Acid (^Aqua fortis). 

Symbol, HN0 3 . — Valency, I. — Molecular weight, 63. 

For specific gravity of solutions and percentage of HN0 3 contained, see Appendix. 

Free or combined HN0 3 may be recognized in solution by 
means of ferrous sulphate. To test for HN0 3 , a small amount 
of the liquid should be taken in a test-tube, and about an equal 
volume of strong H 2 S0 4 added cautiously. The whole should 
then be mixed by means of a glass rod, and cooled quickly by 
placing the tube in water. When cool, a small piece of ferrous 
sulphate should be dropped into the tube, care being taken to 
select a fragment of crystal which is of a clear green color, with 
no powdery whitish substance upon it. If HN0 3 is present, a 
purplish zone will form after a few moments about the fragment 
of ferrous sulphate, while in the absence of HN0 3 , the entire 
solution will remain unchanged. Instead of a fragment of the 
salt, a freshly made solution of ferrous sulphate may be employed. 
By inclining the tube containing the liquid to be tested, the 
ferrous solution may be carefully poured down the side so as not 
to mix with the solution in the tube. On again bringing the tube 
into an upright position, a purple zone will appear at the line of 
junction of the two liquids when HN0 3 is present, and on shaking 
the tube so as to mix the contents, the whole solution will be more 
or less darkened. A few experiments with solutions known to 
contain HN0 3 , in comparison with those known not to contain it, 
will be useful in familiarizing one with the appearance of the test, 
and in enabling one to acquire the moderate skill necessary to 
make it successful. 

Nitric acid in solution, when other free acids are absent, may be 
estimated with standard soda solution, the details of the process 
being precisely the same as in the case of Hydrochloric Acid, which 
see ; the proper amount of solution to be weighed in this case 
being 63 grammes to be diluted to 1000 c.c. 

The estimation of HN0 3 when mixed with other acids, or when 
in combination, presents certain difficulties and calls for special 
apparatus. When this estimation seems called for the sample had 
better be sent to a reliable analyst. 

The impurities to be looked for in commercial nitric acid 
(" aqua fortis ") are hydrochloric and sulphuric acids and 
metals. 



ACTUAL ANALYSIS. 357 



ACETIC ACID. 
Pyroligneous Acid (Wood Vinegar). 

Symbol, C 2 H 4 2 . — Valency, I. — Molecular weight, 60. 
Far specific gravity of solutions and percentage of C 2 H 4 2 contained, see 
Appendix. 

Free acetic acid, unless present in quite small amount, may 
usually be recognized by its vinegar odor, more pronounced on 
warming. When present in too small a quantity to be recogniz- 
able by the above means, or when in combination, it may be con- 
verted into acetic ether, which is a very volatile substance having a 
very distinctive and penetrating though not unpleasant odor. To 
perform the test a small portion of the liquid to be tested is placed 
in a test-tube. About one-half its volume of alcohol is added, 
and an equal amount of strong sulphuric acid, and the whole well 
mixed. If acetic acid (or acetates) were present in the solution, 
the odor of acetic ether will be apparent either at once, or will 
become so on heating the contents of the tube to boiling over a 
lamp. 

In order to familiarize oneself with the odor of acetic ether so 
as to be able to recognize it, it will be well to make the test as 
above upon a solution of sodium acetate containing from 2 to 
5 grammes of the salt in 100 c.c. 

Free acetic acid in solution, apart from other free acids, may be 
estimated by titration with standard soda solution in the manner 
given in detail under Hydrochloric Acid, above. The proper 
amount to be weighed in this case is 60 grammes to be made to 
1000 c.c. The number of cubic centimetres of normal soda solu- 
tion consumed or neutralized by 100 c.c. of the diluted solution 
then equals per cents, of C 2 H 4 2 in the original solution to be 
tested. 

It should be borne in mind that in titrating acetic acid, when 
litmus solution is employed as the indicator of the saturation 
point, soda solution should be added until the liquid is a full blue, 
instead of stopping when the purple tint is reached, as in the 
titration of the acids previously mentioned. 

On this account, we prefer to employ a solution of phenol- 
phtalein as indicator in the present case. To make this solution, 
0.200 grammes (about) of phenolphtalein should be dissolved in 



358 THE CHEMISTRY OF PAPER-MAKING. 

100 c.c. of moderately strong alcohol, and the solution filtered if 
not clear. To this solution weak caustic soda solution is added 
until a very faint rose color remains after shaking. The solution 
is then ready for use. It should be kept well corked. About 10 
to 15 drops of this solution are to be added to the portion of acid 
solution used for the titration. The soda solution should -then 
be added until a brilliant rose purple coloration appears which 
remains permanent after stirring. This indicates that the acid 
has all been neutralized, since the color only appears in the 
presence of alkali, but the presence of even the most minute 
quantity of free alkali is sufficient to develop a brilliant color. 
For the estimation of acetic acid in combination, see Acetates. 

Impurities in commercial acetic acid are muriatic acid, acetates 
of soda and lime, acetate of methyl, and empyreumatic (organic) 
matter. 

Oxalic Acid. 
Symbol, H 2 C 2 4 , 2 H 2 0. — Valency, II. — Molecular weight, 126. 

Oxalic acid free, or in combination with alkalis, may be recog- 
nized in solution by means of calcium sulphate solution. The 
solution to be tested should be rendered alkaline by the addition 
of ammonia in excess. It is then filtered if necessary, and solution 
of calcium sulphate added. If oxalic acid, or an oxalate, is present, 
this will produce a fine white cloud or precipitate easily redissolved 
by hydrochloric acid in excess, and again appearing on addition of 
excess of ammonia water. Free oxalic acid may be estimated 
by titration with standard soda solution as in the preceding 
paragraphs. 

The proper amount of the solution to be weighed is 63 grammes 
to be made to 1000 c.c. 

If the crystallized acid is to be tested, it is as well to weigh one- 
half the above amount, and make to 1000 c.c, and take 100 c.c. of 
this solution for titration. Of course, in this case the number of 
cubic centimetres of normal soda used must be doubled to give 
the percentage of actual crystallized acid in the sample. 

Either litmus or phenolphtalein solution may be employed as 
indicator with oxalic acid, and no precautions need be taken to 
nearly neutralize with soda solution before heating as in the case 
of hydrochloric and nitric acids, since this acid is not in the 



ACTUAL ANALYSIS. 359 



least volatile from its solution, as is the case with the acids last 
mentioned. 

ALKALIS AND ALKALINE EARTHS. 

Unite with acids to form salts. — Solutions of the alkalis turn litmus blue. 

Sodium Hydrate {Caustic Soda~). 

Symbol, NaHO. — Valency, I. — Molecular weight, 40. 

For specific gravity of solutions and percentage of NaHO contained, see Appendix. 

It is difficult to apply tests to a solution of caustic soda or of 
soda salts which shall give direct evidence of the presence of soda 
as distinct from other alkalis. Perhaps the best ready qualitative 
test for soda lies in the intense yellow color given to the flame of 
an alcohol lamp or Bunsen burner when a platinum wire moistened 
with the solution to be tested is held in the flame. This test is, 
however, of such extreme delicacy, and the presence of compounds 
of soda in the minute quantities required to produce the yellow 
flame so well-nigh universal, as to render this test of little practical 
value. Probably the easiest way to prove the presence of soda in 
an alkaline solution is to work backwards and prove that it is not 
one of the other alkalis (appropriate tests for which will be 
described under their respective heads), and consequently must be 
soda. 

There are several direct tests which can be applied to prove the 
presence of soda or its salts ; but as they require very careful 
manipulation to render their indications reliable, we have thought 
it best not to describe them here. 

Quantitative. — In a simple solution of caustic soda not con- 
taining other alkalis the percentage of soda, NaHO, may be easily 
determined by titration with standard acid solution. For this 
purpose a standard sulphuric acid of about normal strength 
(49 grammes H 2 S0 4 per litre) is perhaps best. Standard oxalic 
acid also answers the purpose well. 

Forty grammes of the soda solution or the solid substance caustic 
soda are to be weighed, and its solution made to 1000 c.c; 100 c.c. 
of this solution is, if not entirely clear, filtered through a dry filter, 
since, if the filter were previously wet with water, it would dilute 
to a certain extent the 100 c.c. passed through it. The filtrate is 
transferred to a beaker or casserole and colored with litmus solu- 



360 THE CHEMISTRY OF PAPER-MAKING. 

tion. Standard acid is run in from the burette until the original 
blue color changes to purple. The liquid is then boiled, when the 
blue color will generally again appear. Acid is again dropped in 
from the burette, a drop at a time, boiling for a moment after each 
addition, until the liquid shows a full red color, and no trace of 
blue or purple appears after two or three minutes' boiling. 

The number of cubic centimetres of acid employed, reduced to 
normal cubic centimetres by the use of the appropriate factor, 
represents the percentage of caustic soda, NaHO, in the sample 
tested. 

In commercial transactions caustic soda is usually quoted as 60 
or 70 per cent, alkali, as the case may be. 

In this connection, as in the alkali trade generally, the term 
" alkali " does not have its proper chemical significance, but signi- 
fies sodium oxide, Na 2 0, or we may call it anhydrous caustic soda. 

31 parts by weight of this substance, Na 2 (" alkali") + 9 parts of 
water = 40 parts of sodium hydrate or caustic soda. 

This being the case, if we wish to find the per cent, of "alkali," 
Na 2 0, in the sample tested as above, we must multiply the per 
cent, of caustic soda, NaHO, by 31 and divide the product by 40. 
%(NaHO)x31 = %(Na2 o. )? or „ alkali< „ 

In Europe an arbitrary custom obtains of using the old numbers 

32 and 41 in place of the corrected ones 31 and 40 respectively in 
all instances mentioned above. This is now entirely without right 
or reason, and is oftentimes annoying to the American buyer, who 
finds a caustic reported as 72 per cent, alkali by the English 
chemist will be reported only 69.75 per cent, by the American 
test, which gives its true value. Of course, when one is aware 
of the custom, it is easy to make the allowance ; but in the 
interests of truth and fair dealing, every American buyer of alkali, 
either caustic or carbonated, should insist that payment be made 
on the basis of the American test. 

The total amount of soda, Na 2 0, present in a given solution, 
both as caustic and as salts of soda, is determined by means of a 
long and somewhat troublesome series of eliminations, by means 
of which the soda is finally obtained in the form either of .pure 
sulphate or chloride, which may be weighed after ignition, and 
from its weight the soda calculated. 



ACTUAL ANALYSIS. 361 



Potassium Hydrate {Caustic Potash}. 

Symbol, KHO. — Valency, I. — Molecular weight, 56.1. 

For specific gravities of solutions and per cent, of KHO, see Appendix. 

Potash may be recognized in solution by means of the color it 
imparts to the colorless Bunsen or alcohol flame. The color, 
except when the proportion of potash is very large, is usually 
masked to the naked eye by the intense yellow color of the sodium 
flame. By the use of a piece of blue (cobalt) glass of a moderately 
deep shade the yellow color of the sodium flame may be shut out, 
as it were, and the potash flame then appears through the glass of 
a beautiful rose color. The manner of applying the flame test is 
to dip the end of a small platinum wire in the solution to be 
tested, and then hold it in the flame until it becomes red hot. 

Caustic potash in solutions not containing other free alkalis 
may be estimated by titration with standard acid in exactly the 
same way as caustic soda described above. 

The amount to be weighed out is 56.1 grammes, to be diluted 
to 1000 c.c. The number of normal cubic centimetres of acid con- 
sumed by 100 c.c. of this solution equals per cents, of KHO. 

If the percentage of K 2 anhydrous potash is required, it may 
be obtained by multiplying the per cents, of KHO by 47.1, and 
dividing the product by 56.1. 

The process of determining accurately the total amount of 
potash in a solution containing salts of potash along with other 
substances, as with soda, is long and tedious to one not thoroughly 
conversant with chemical manipulations, and on that account we 
omit it here. 

AMMONIUM HYDRATE. 

Ammonia (Water of Ammonia}. 
Symbol, NH 4 OH. 

Ammonia is usually reckoned and reported in terms of anhy- 
drous ammonia gas ; and in accordance with this custom we shall 
so consider it in this paragraph. 

Symbol, NH 3 . — Valency, I. — Molecular weight, 17. 

For tables of specific gravity of solutions and percentage of ammonia contained, see 
Appendix. 

Free, or caustic, ammonia, being a volatile alkali, reveals its 
presence, either at once, or on warming the solution, by its char- 



362 THE CHEMISTRY OF PAPER-MAKING. 

acteristic odor, and by turning a piece of filter paper, moistened 
with red litmus solution, blue, when held in the vapor arising 
from a warmed solution. It does not reveal its presence in this 
way when present in combination with an acid ; but on the addi- 
tion of a sufficient quantity of caustic soda solution to a solution 
containing any salt of ammonia it may be at once detected, as 
indicated above. 

Caustic ammonia in solution not containing other free alkalis 
or alkali carbonates, may be titrated directly with standard acid, 
as indicated under Soda, above. 

Ammonia being a volatile alkali, however, the solution must 
be titrated without heating. 

The proper amount to be weighed out is 17 grammes to 1000 c.c. 

For the determination of the combined ammonia in any liquid, 
it is sufficient, after having made up to 1000 c.c. as above, to take 
100 c.c. and distil after adding an excess of magnesium oxide 
(caustic magnesia), MgO, so long as any ammonia continues to 
come over with the steam. This usually takes from one to two 
hours. The distillate is to be received in a flask containing a 
measured number of c.c. of standard acid which must be more than 
sufficient to neutralize all the ammonia which may distil over. 
When all the ammonia has been distilled into the acid, the excess 
of acid remaining unneutralized is titrated by means of standard 
soda and litmus — the difference between the number of normal 
cubic centimetres of acid employed and the number of normal 
cubic centimetres of soda used to neutralize the excess remaining 
equals the number of normal cubic centimetres of acid neutralized 
by the ammonia, or per cents, of NH 3 in the sample. 

Calcium Hydrate (Slaked Lime'). 

Symbol, CaH 2 2 . — Valency, II. — Molecular weight, 74. 

Tor specific gravity of solutions and milk of lime, see Appendix. 

Calcium Oxide. — Lime (Caustic Lime). 

Symbol, CaO. — Valency, II. — Molecular weight, 56. 

The term " lime " or " caustic lime," as commonly employed, 
means burned lime or calcium oxide, CaO, in distinction from 
slaked lime, which is calcium hydrate, CaH 2 2 , or the former 
combined with water. 



LIME. 363 

Lime may be recognized in solution by means of oxalate of 
ammonia solution with which it gives a fine white crystalline pre- 
cipitate (compare Oxalic Acid, above). The solution to be tested 
should first be rendered alkaline with ammonia, filtered if ammonia 
has caused a precipitate, and the filtrate tested with a few drops 
of oxalate of ammonia. 

If metallic salts, as lead acetate or zinc sulphate or chloride, 
are present, the metallic oxides must be removed by treatment of 
the solution, after the addition of ammonia, with ammonium sul- 
phide solution and filtering. The filtrate is then tested with oxalate 
as above. A good method for testing a sample of burned lime or 
limestone, which is easily carried out and which with care will 
give results sufficiently accurate for all ordinary purposes, is as 
follows. A considerable amount, say a pound or two, of the lime 
should be picked out to represent as fairly as possible the average 
quality of the lot. This should be broken down into small bits 
not larger than peas. The whole is then well mixed, and an 
ounce or two taken out for the working sample. This small 
sample should be ground in a porcelain mortar sufficiently fine to 
pass a No. 24 sieve, and the resulting powder again well mixed 
and preserved in a well-closed bottle. 

For the actual analysis, 5 grammes of the powder are to be 
weighed out and transferred to a beaker; about 50 c.c. of water 
are then poured on it, and sufficient hydrochloric acid to dissolve 
the sample (about 25 c.c. will be sufficient), and the whole boiled. 
This treatment will dissolve the entire sample with the exception 
of the silica, Si0 2 , which is to be filtered out on a small filter, well 
washed with hot water, dried, transferred to a platinum crucible 
together with the filter, and ignited strongly, and after cooling 
weighed. 

The weight found calculated to per cents, gives sand and silica, 
insoluble in acid, in the sample. 

The solution filtered from the above, together with the washings 
from the same, is next to be heated, and ammonia water added 
cautiously until the odor of ammonia is just perceptible in the 
liquid after stirring. The solution is then to be kept very near 
to the boiling-point for some time until all the smell of ammonia 
has disappeared. This treatment separates the alumina and 
sesquioxide of iron present. The solution is next to be filtered, 
and the precipitate well washed with hot water. The residue of 



364 THE CHEMISTS Y OF PAPER-MAKING. 

A1 2 3 and F 2 3 on the filter is to be thoroughly dried and then- 
ignited in the platinum crucible, together with the filter, and 
weighed after cooling, and the weight calculated into per cents. 

The filtrate and washings from the alumina and iron oxide 
precipitate is next made to 500 c.c. Then 50 c.c. of this, which 
equals 0.5 grammes of the original sample, is transferred to the 
platinum evapo rating-dish, which has been previously cleaned, 
ignited, and weighed. The contents of the dish are evaporated to 
dryness on the water-bath, and ignited (carefully, to avoid spatter- 
ing and consequent loss) at a moderate heat until no more fumes 
come off. The dish is then cooled and a small amount of water 
added, together with two or three drops of hydrochloric acid. 
When all is dissolved, about 30 to 40 drops of strong sulphuric 
acid is added, and the whole again evaporated to dryness and 
ignited until no more fumes appear, and finally brought to a 
full red heat. It is absolutely necessary at this point that fumes 
do appear, otherwise it will be necessary to again add water with 
a few drops more sulphuric acid, evaporate, and ignite. 

The residue in the dish now consists of the lime and magnesia 
present in the portion of the sample taken (with possibly some- 
times traces of soda and potash, which may be here disregarded), 
now in the form of anhydrous sulphates. The residue here 
obtained should be of a pure white color. It is cooled in a desic- 
cator and weighed as rapidly as possible, as, if there is much 
sulphate of magnesia present, it will rapidly absorb moisture from 
the air and gain in weight. Deducting the weight of the dish 
leaves the combined weights of the sulphate of lime and sulphate 
of magnesia, which can be formed from the amount of the sample 
taken for this estimation, 0.5 grammes. 

After weighing, the substance in the dish is transferred by the 
aid of a little water from the washing-bottle to a small beaker. 
Any adhering particles may be removed by rubbing with the clean 
tip of the finger, and should afterward be rinsed into the 
beaker. Any lumps should be broken down with the end of a 
glass rod. Two or three drops of hj^drochloric acid are next 
added and the solution well stirred. An undissolved portion will 
almost always remain. Next about two drops of sulphuric acid 
are added and stirred. Strong alcohol is next added equal in 
bulk to about twice the volume of the liquid in the beaker, the 
whole well stirred and allowed to stand, with occasional stirring, 



MAGNESIA. 365 



f-or two hours or more. It is then to be filtered and the filter 
washed two or three times with a mixture of two volumes of 
strong 1 alcohol and one volume of water. It is then washed with 
a mixture of equal volumes of alcohol and water as long as the 
washing continues to remove anything, which may be ascertained 
by allowing a drop or two to fall from the funnel on a clean 
watch-glass and then evaporating it by gently moving the glass. 
If no appreciable residue is left on the glass, the washing may be 
considered finished. We now have on the filter all the lime as 
sulphate of lime, and ail the magnesia in the solution. It only 
remains, then, to dry and ignite the precipitate of sulphate of 
lime and calculate the lime in it. 

Sulphate of Lime (CaS0 4 ) x 0.4118 = Lime (CaO). 

We next subtract the actual sulphate of lime, weighed as above, 
from the weight of the mixed sulphates of lime and magnesia 
found previously, the difference being sulphate of magnesia, which 
multiplied by 0.3333 = magnesia, MgO. 

A good lime for building purposes or for causticising should be 
almost entirely free from magnesia. For the best results in mak- 
ing sulphite liquor it should carry at least 35 per cent, of mag- 
nesia. 

Magnesium Hydrate. 
Symbol, MgH 2 2 . 

Magnesia. 
Symbol, MgO. — Valency, II. — Molecular weight, 40. 

The remarks above, in regard to calcium hydrate and lime, at 
the beginning of the last section, apply equally to magnesium 
hydrate and magnesia. 

Magnesia is recognized in solution by means of solution of 
phosphate of soda. The solution to be tested must contain no 
metallic salts other than those of iron and alumina. Some am- 
monium chloride is first added to the solution, then ammonia in 
excess, the liquid boiled and filtered from the alumina and sesqui- 
oxide of iron precipitated. Oxalate of ammonia is added to the 
filtrate in considerable amount, and if a precipitate appears, the 
liquid is heated in a water-bath, and again filtered. More ammonia 



366 THE CHEMISTRY OF PAPER-MAKING. 

is added to the filtrate, and some phosphate of soda solution, and 
the liquid well stirred with a glass rod, allowing the rod to rub 
the sides and bottom of the glass. If magnesia is present, a pre- 
cipitate soon appears as a fine, white crystalline powder, which 
soon settles, leaving the liquid clear. If very little MgO is pres- 
ent, it may appear only after a little time, and then only as white 
streaks at those places where the rod has marked the glass in 
stirring. If metallic salts are present, the slightly acid solution 
must first be treated with sulphuretted hydrogen gas, by bubbling 
the gas through the solution until it smells strongly of the gas 
after shaking. It is then to be filtered, and to the filtrate some 
ammonia is added, and then ammonium sulphide as long as the 
latter causes a precipitate. The liquid is again filtered, and an 
excess of oxalate of ammonia is added, to separate lime present. 
After warming for some time, the liquid is filtered from the lime 
precipitate, and is then ready, after cooling, to be tested for mag- 
nesia with phosphate of soda, after the manner first described. 

Quantitative. — Magnesia is estimated by weighing it as mag- 
nesium pyrophosphate, Mg 2 P 2 7 . This substance multiplied by 
0.3604 gives the equivalent weight of magnesia, MgO. 

The solution in which MgO is to be determined must be freed 
from all other substances except soda and potash and ammonia, 
as described above. To the solution thus prepared a large excess 
of ammonia is added, and phosphate of soda solution in excess. 
The liquid is well stirred, taking care, in this case, to avoid touch- 
ing the sides and bottom of the glass with the rod, since this 
will cause the precipitate to adhere to the glass. The beaker is 
then covered, and allowed to rest for at least two hours. It 
is then filtered, and the precipitate rinsed on to the filter by the 
aid of a wash-bottle filled with water 8| parts, and ammonia, 
strong, 11 parts. It is necessary to employ this dilute ammonia 
for washing, instead of water, as the latter would dissolve the 
precipitate. The precipitate should be washed until a drop of 
the washings, to which a drop of nitric acid has been added, gives 
no cloud on the addition to it of a drop of a solution of silver 
nitrate. After the precipitate is thoroughly washed, it is dried, 
and transferred, as carefully as may be, to a small crucible (plat- 
inum by preference, though porcelain will answer), and ignited 
to a full red heat. The filter, with the remainder of the precipi- 
tate adhering, is then thrown into the crucible and ignited, until 



CARBONATES. 367 



the carbon of the filter is entirely consumed, and the whole of a 
bright red heat. It is then cooled and weighed ; and the weight 
of the precipitate multiplied by 0.3604 gives the actual weight of 
MgO in the portion of the sample operated on. 

CARBONATES. 

COMPOUNDS OF BASIC (ALKALINE) OXIDES WITH CARBONIC ACID. 

Those which are soluble in water, carbonates of soda, potash, 
and ammonia, give solutions which show an alkaline reaction with 
litmus. All are decomposed by acids in general with liberation of 
carbonic acid gas and formation of that salt of the base correspond- 
ing to the acid employed. 

SODIUM CARBONATE. 

Sal Soda — Soda Crystals {Washing Soda} — Soda-Ash. 

For specific gravity of solutions and per cent, of the salt contained see Appendix. 
Soda crystals, or washing soda, is crystallized carbonate of soda. 
Symbol, Na 2 C0 3 , 10 aq. — Valency, II. — Molecular weight, 286. 

Carbonates of soda, potash, and ammonia all agree in being solu- 
ble in water ; their solutions effervesce on the addition of an acid, 
and all give a white precipitate with solution of calcium chloride. 
Solution of ammonium carbonate is, however, distinguished from 
the other two by the strong smell of ammonia developed on the 
addition of caustic soda solution and warming. Carbonates of 
soda and potash are distinguished by the flame reaction (see under 
Caustic Potash), best applied after adding a slight excess of hydro- 
chloric acid. 

Soda-Ash. 
Symbol, Na. 2 C0 3 . — Valency, II. — Molecular weight, 106. 

Soda-ash (Solvay) is nearly pure and nearly anhydrous carbonate 
of soda. Soda-ash may be formed from soda crystals by furnacing, 
which in this case serves simply to drive off, or dry out, the 
combined water, 10 aq., of the crystals ; conversely, soda crystals 
are made from ash by simply dissolving and allowing to crystallize. 

The amount of " alkali," Na 2 0, in soda-ash or crystals may be 
estimated by titration with standard acid. 



368 THE CHEMISTRY OF PAPER-MAKING. 

The proper amount to be weighed out for this purpose so that 
the number of normal cubic centimetres of acid consumed shall 
read per cents, of alkali direct is 31 grammes. This is to be dis- 
solved, and the solution made to 1000 c.c. 100 c.c. of this solu- 
tion are to be filtered through a dry (wet with the solution, and 
not with water) filter and titrated, the solution being colored with 
litmus solution, as under Caustic Soda (which see), the only addi- 
tional precaution being to continue the boiling after the addition 
of acid sufficiently long to make sure that a red color has been 
obtained, which will not turn to blue or violet on longer boiling. 

The percentage of carbonate of soda may be calculated to 
that of alkali by the proportion 

Na 2 Na 2 C0 3 

62 : 106 = % Na 2 found : x, 

and the percentage of soda crystals equivalent to the alkali found 
by the proportion 

Na 2 Na 2 C0 3 10 aq. 

62 : 286 = % Na 2 found : x. 

The soda-ash of the market is classified as carbonated or caustic 
ash, according as all the alkali in it exists as carbonate, or part as 
carbonate and part as caustic soda. The testing of carbonated 
ash for technical uses is commonly limited to the determination 
of the total alkali, Na 2 0, it contains. Sometimes, however, in 
old process or " Leblanc " ash an estimation of the sulphate of 
soda may be useful, since for use in the manufacture of "soda 
pulp " a small percentage of sulphate of soda in the ash purchased 
is rather an advantage than otherwise. 

The percentage of sulphate of soda present is easily calculated 
from the percentage of sulphuric anhydride, S0 3 , contained. 

This latter is determined as follows : — 

100 c.c. of the solution prepared for titration, filtered as before 
through a dry filter, are transferred to a beaker, and hydrochloric 
acid cautiously added as long as each addition produces effer- 
vescence. A few drops more are added to render the solution 
strongly acid, and the solution covered with a glass and heated 
to boiling. Barium chloride solution is then added so long as it 
produces a precipitate, and the whole allowed to stand in a warm 
place until the precipitate has settled and the solution above it 



CARBONATES. 369 



become clear. The solution is then poured carefully on to a filter, 
taking care to disturb the precipitate as little as possible while 
pouring out the liquid. After all the liquid has passed through 
the filter, the precipitate is transferred to the filter by the aid of 
a wash-bottle filled with hot water, and the filter precipitate thor- 
oughly washed with the water. It is then dried, transferred to the 
platinum crucible, the filter carefully folded and added, and the 
whole strongly ignited. The weight of the ignited barium sul- 
phate, BaS0 4 , multiplied by 0.3433, equals sulphuric anhydride, 
S0 3 , which may then be calculated into per cents, of' the original 
ash. 

The equivalent sulphate of soda may be found by the proportion 

S0 3 N"a 2 S0 4 

80 : 142 = c? of S0 3 : x % of Na 2 S0 4 , sulphate of soda, 

and the percentage of alkali, Na 2 0, which it can furnish on con- 
version by the proportion 

Na,S0 4 Na a O 

142 : 62 = °J sulphate of soda : £ (% of equivalent alkali). 

Caustic Ash. 

The total alkali, Na 2 0, in caustic ash and the sulphate present 
are to be estimated exactly as in carbonated ash just described. 
In addition to these determinations, however, a knowledge of the 
actual caustic alkali present is necessary to fix upon the value of 
the ash. This is determined as follows. 

250 c.c. of the solution prepared for titration of the total alkali 
is transferred to a 500 c.c. flask, and the small flask well rinsed 
into the larger, using as little water as practicable for the purpose. 
A strong solution of barium chloride is then added, witli shaking 
so long as it produces a precipitate. A little more of the barium 
chloride is added, and the flask filled to the mark with water and 
well shaken. 

The flask is corked and allowed to rest until the white precipi- 
tate has settled and the solution above has become clear. 100 c.c. 
of this solution are then filtered through a dry filter, the funnel 
being kept covered with a glass during the filtration. This 
solution (100 c.c.) is then transferred to a beaker or dish, and 
litmus added and titrated with standard acid. 



370 THE CHEMISTRY OF PAPER-MAKING. 

It is not necessary to heat the solution during this titration. 
The number of normal cubic centimetres of acid employed multi- 
plied by two, since the 100 c.c. of the last solution is equal to only 
50 c.c. of the original solution prepared, gives the percentage of 
alkali, Na 2 0, existing as caustic soda, NaHO, in the sample. 

Black Ash. 

This is a soda-ash containing a greater or less amount of finely 
divided carbon, from which it derives its black or dark gray color. 
It also contains ordinarily small amounts of sulphide of soda, 
which is formed from any sulphate which may have been present 
before furnacing the latter, being reduced by the carbon or organic 
matter at the high temperature of the furnace. 

The valuation of black ash for technical purposes is, in most 
cases, limited to a determination of its total alkaline strength by 
titration, as under Soda-ash, above. This would include the alkali, 
Na 2 0, present as sulphide as well as that present as actual car- 
bonate. In testing a well-burned black ash no variation will be 
found to be necessary from the method given above for the titra- 
tion of soda-ash, as the 100 c.c. of liquor filtered out for the 
test will be found to be practically colorless. If, however, the 
sample of black ash has not been thoroughly burned, the filtered 
solution may be quite dark, or even black, in color from partially 
carbonized matter dissolved. 

In this case the simplest way out of the difficulty, perhaps, is 
to throw away the solution already prepared, and weigh out a 
new lot of 31 grammes. This is then transferred to a platinum 
dish (best to the evaporating-dish) and thoroughly ignited over 
the lamp. The whole is then transferred to the litre flask, the 
dish well rinsed in, and after the ash is dissolved made to the 
mark as before. If the ignition has been Avell performed, a suf- 
ficiently colorless solution will be obtained on filtering. The com- 
plete analysis of black ash is a problem of so complicated a nature 
as to be best performed by the professional chemist. Not infre- 
quently, however, such an analysis may serve to point out an 
erroneous method of practice, or an avoidable waste in the manu- 
facture, of which this black ash is a bye-product. 



CABBONATES. 371 



Bicarbonate of Soda (Baking-Soda). 
Symbol, NaHC0 3 . — Valency, I. — Molecular weight, 84. 

This salt is much less soluble in water than the carbonate of 
soda. Its reactions in general are similar to those of the neutral 
carbonate, but less strong. 

It contains about one-half as much alkali, Na 2 0, as the simple 
carbonate, and about twice as much carbonic acid. On this 
account, and on account of its being very mildly alkaline, it is 
always employed in all baking-powders as the source of the gas 
required to " raise " the bread. 

The testing of bicarbonate of soda requires a determination of 
the total alkali, Na 2 0, and also a determination of the total 
carbonic anhydride, C0 2 (commonly called carbonic acid), present. 
From the data furnished by the two determinations, the actual 
amounts of bicarbonate and of carbonate of soda present may be 
calculated. Bicarbonate made by the " Solvay Process " also 
contains a small percentage of ammonia in combination with 
carbonic acid. When present, ammonia must also be determined. 

The total alkali in bicarbonate, free from ammonia, may be 
determined by titration with standard acid. 

3.100 grammes of the substance are to be weighed, transferred 
to a beaker or dish with about 100 c.c. of water, litmus added, 
and titrated direct with acid, care being taken to thoroughly boil 
the solution during the titration. The number of normal cubic 
centimetres of acid used gives the per cents, of alkali, Na 2 0, 
present. 

When ammonia is present, the sample weighed out for the titra- 
tion must be ignited for some time at a moderate heat, which will 
expel all the ammonia, before dissolving it for titration. 

The estimation of carbonic acid is conducted in a special form 
of apparatus, called the " Schroetter Carbonic Acid Apparatus." 
The use of this apparatus is as follows : The apparatus being clean 
and dry, 2 grammes to 5 grammes of the substance to be examined 
is weighed and transferred very carefully to the small flask forming 
the base of the apparatus. About 10 c.c. of water is then added 
and the cork carefully inserted. The stopcock between the 
flask and the bulb-tube directly above it is closed, and the bulb 
filled with hydrochloric or nitric acid, the neck carefully wiped, 



372 THE CHEMISTRY OF PAPER-MAKING. 

and its stopper inserted. The other large bulb is next rilled about 
one-half full of strong sulphuric acid, the neck wiped, and the 
stopper inserted. The whole apparatus with its contents is now 
weighed carefully and the weight recorded. The cock is next 
opened slightly so as to allow the acid in the bulb to very slowly 
drip into the flask. This at once frees carbonic acid gas from the 
carbonate there contained, which is forced to bubble through the 
bulb containing sulphuric acid. This acid serves to remove and 
retain all moisture which may be carried up by the gas, so that only 
pure, dry C0 2 gas finally escapes from the apparatus. After 
making certain that sufficient acid has been allowed to enter the 
flask to decompose the whole of the carbonate present, the cock is 
closed, and the contents of the flask heated cautiously to boiling 
and allowed to boil until steam commences to be driven over into 
the bulb containing the sulphuric acid. It is then removed from 
the heat and the cock at once opened to allow the remaining acid 
to run in or air to be drawn into the flask as the steam condenses 
and the apparatus allowed to become cold. It is then once more 
weighed, and this weight deducted from the previous weight leaves 
the loss of weight during the operation, which, if sufficient care has 
been employed, represents the weight of carbonic anhydride, C0 2 , 
in the amount of substance operated upon. This weight may be 
easily figured into per cents. 

The method of procedure described above may serve for the 
estimation of carbonic acid, C0 2 , in any carbonate. The ammonia 
present in Solvay bicarbonate may be determined by placing a 
weighed amount, say about two or three grammes, of the bicar- 
bonate in a tube of hard glass about six inches in length and a 
half-inch in diameter, known as an ignition tube. A loose plug 
of asbestos is placed near the mouth of the tube, which is fitted 
with a good cork. This in turn carries a piece of glass tube, 
passing just through the cork into the combustion tube, and bent 
downward in front of the tube, so as to pass through a cork fitted 
into one end of a U-tube. Two or three cubic centimetres of 
standard acid, accurately measured from a burette, are placed in 
the U-tube and colored with litmus. Enough water should be 
added so that the liquid in the tube may well cover the bend 
of the tube. The ignition tube should be held by a clasp in a 
nearly horizontal position and a gentle heat applied for some time 
to the portion of the tube containing the carbonate, and gradually 



CARBONATES. 373 



increased, nearly to redness. This will expel all the ammonia 
present, which will be driven into the U-tube, and there absorbed 
by the acid contained therein. 

When no more bubbles are seen to pass through the liquid in 
the U-tube, and the substance in the ignition tube is very nearly 
or quite red hot, the connection between the two tubes may be 
broken and the lamp removed. 

The liquid should next be transferred from the U-tube to a 
beaker, and the tube carefully rinsed, and the acid remaining in 
the liquid unneutralized titrated with standard soda. The number 
of normal cubic centimetres of soda employed, taken from the 
number of normal cubic centimetres of acid originally placed in 
the U-tube, leaves the normal cubic centimetres neutralized by 
the ammonia from the sample of bicarbonate weighed. This 
latter number multiplied by 0.017 will give the weight of 
ammonia, NH 3 , obtained from the sample operated on, and this 
weight may be readily calculated into equivalent per cents. 

If 1.7 grammes of the sample be weighed for the experiment, 
the number of normal cubic centimetres of acid neutralized by the 
ammonia driven off as above will represent per cents, of NH 3 in 
the sample analyzed. 

Carbonate of Potash (Pearlash — Salt of Tartar). 
Symbol, K 2 C0 3 . — Valency, II. — Molecular weight, 138.2. 

This substance, though formerly much used in the arts, is now 
almost entirely discarded in favor of soda-ash, which has been 
found to answer the required purpose in a large majority of cases 
equally, as well as the potash salt, and to offer in very many 
instances many advantages over the latter, not the least of which 
is its greater cheapness. 

The methods for testing pearlash are precisely similar to those 
given in detail under Carbonate of Soda, which see. 

The proper amount of pearlash to be weighed out for titration 
is 47.1 grammes to be made to 1000 c.c, and 100 c.c. employed for 
the test. The normal cubic centimetres used will then represent 
per cents, of potash, K 2 0, present. 



374 THE CHEMISTRY OF PAPER-MAKING. 

CARBONATE OF LIME. 

Chalk (French White — Whiting — Marble — Limestone). 
Symbol, CaCO s . — Valency, II. — Molecular weight, 100. 

Almost entirely insoluble in pure water — water containing 
alkaline salts and carbonic acid dissolves it in somewhat larger 
amounts. 

The test required for chalk, French white, or whiting, is usually 
one for purity alone, and consists in dissolving a portion in dilute 
hydrochloric acid. A pure article should be entirely dissolved 
by the acid — absence of sand, or silicates (clay). The solution 
is next tested with barium chloride for presence of sulphates. 
A complete analysis of marble and limestone is frequently re- 
quired. This may be performed with sufficient accuracy for most 
technical purposes in exactty the same way as described for the 
the analysis of Lime above, which see. 

The carbonic acid, C0 2 , may be determined by the aid of the 
Schroetter apparatus, described above, when desired. 



CARBONATE OF MAGNESIA. 

Magnesite. 
Symbol, MgC0 3 . — Valency, II. — Molecular weight, 84. 

This substance is worth noting as being the crude base employed 
in making the solution used in the " Ekman Sulphite Pulp Pro- 
cess." An analysis of this substance for technical purposes may 
be made precisely as directed for the analysis of limestone. The 
precaution, however, must be taken of weighing the ignited sul- 
phates with the dish containing them covered with a glass, and the 
weighing must be performed as rapidly as possible, since ignited 
magnesium sulphate absorbs moisture very rapidly from the air, 
and increases in weight in consequence. 

The ignition of the sulphates also should not be prolonged 
beyond the time necessary to expel all the free sulphuric acid 
or the heat raised beyond a moderate red heat, since sulphate 
of magnesia is not absolutely unalterable under prolonged and 
intense ignition. 



SULPHATES. 375 



CARBONATE OF ZINC. 

Symbol, ZnC0 3 . — Valency, II. — Molecular weight, 125. 

Impurities to be looked for : lead and lime carbonates, and sul- 
phate of lime and insoluble matter. 

The substance to be examined should be dissolved in hydro- 
chloric acid, in which, if pure, it will be completely soluble. The 
solution nearly neutralized with carbonate of soda, but still dis- 
tinctly acid, is treated with sulphuretted hydrogen by bubbling 
the gas through for a little time — any blackening of the solution, 
or the appearance of a black precipitate, indicates the presence 
of lead. 

The solution, filtered if necessary, should then be rendered 
ammoniacal, and sulphide of ammonia added (best to the boiling 
solution) so long as it continues to cause a precipitate. The solu- 
tion, filtered from this precipitate, may be tested for lime with 
oxalate of ammonia solution, as previously described. 

SULPHATES. 

The sulphuric acid in sulphates is always determined in the 
same way ; namely, by precipitating it by means of barium chlo- 
ride solution from the solution rendered acid by hydrochloric acid, 
and weighing the barium sulphate produced. 

For the details of the manipulation, see estimation of sulphate 
of soda in Soda-Ash. 

ALUM. 

Potash Alum, K 2 A1 2 4 S0 4 , 24 H 2 0. — Molecular weight, 948. 

Soda Alum, Na 2 Al 2 4S0 4 , 24H,0. — " " 916. 

Ammonia Alum, (NH 4 ).,A1 2 4S0 4 , 24H 2 0. — " " 906. 

Sulphate of Alumina, Al 2 3 S0 4 , 18 H 2 0. — " " 666. 

Since the value of all alums for paper-makers' purposes depends 
on the amount of combined alumina they contain, and on the 
absence of free acid, of iron and of insoluble matter, it becomes 
necessary for our present purpose to give methods for the deter- 
mination of these four things only. 

The presence or absence of iron may be determined by the use 
of ferrocyanide of potash. For this purpose a considerable 



376 THE CHEMISTRY OF PAPER-MAKING. 

amount of alum should be dissolved in a moderate quantity of 
water, and the solution heated to boiling after the addition of a 
few drops only of nitric acid. The solution is then allowed to 
cool, and some freshly made solution of ferrocyanide of potash 
(yellow prussiate) added. If iron is present, a blue color will be 
developed of greater or less depth, according as there is more or 
less iron present. If no iron is present, the solution will remain 
colorless. 

Many methods have been proposed for testing an alum directly 
for the presence of free acid, but in our hands none have proved 
entirely satisfactory. 

For the valuation of an alum, then, we may proceed as follows : 
Weigh out 25 grammes and dissolve in about 200 c.c. of warm 
water. When all is dissolved, filter from any insoluble matter 
into a 500 c.c. measuring-flask and wash the residue on the filter 
thoroughly with hot water. This residue dried, ignited, and 
weighed, gives the insoluble matter in the 25 grammes taken. 

The filtered solution is next made (after cooling) to 500 c.c. and 
well mixed. 100 c.c. of this solution, equivalent to 5 grammes 
of the alum, are again made to 500 c.c. (solution No. 2). 

100 c.c. of the latter (solution No. 2), equivalent to 1 gramme 
of the alum, is taken for the estimation of total sulphuric acid 
present by precipitation with barium chloride (see Sulphate in 
Soda- Ash). 

100 c.c. of solution No. 2 is also taken for the determination 
of alumina. This is diluted to about 400 c.c. in a beaker, and 
some ammonia chloride solution added. It is then heated nearly 
to boiling and ammonia solution added, drop by drop, until the 
smell of ammonia can just be distinctly detected in the solution. 
It is then heated to just below the boiling-point for some time, 
until the odor of ammonia can no longer be detected in the solu- 
tion. The volume of the solution should be kept nearly the same 
by the addition of hot water from time to time as the solution 
evaporates. This treatment precipitates all the alumina as well 
as all the sesquioxide of iron present in the form of the hydrated 
sesquioxides of alumina and of iron, a very bulky, gelatinous pre- 
cipitate, white if no iron is present, but more or less colored if 
iron is present. The precipitate should be allowed to settle and 
the clear liquor carefully decanted through a good-sized filter. 
Water is added to the precipitate in the beaker and brought to a 



SULPHATES. 377 



boil. It is again allowed to settle, and decanted through the 
same filter as before. The boiling up with water and decanting is 
best repeated a second time, and finally the precipitate is trans- 
ferred to the filter and washed thereon with hot water until a 
drop of the washings gives at most only a very slight cloud when 
tested on a glass with a drop of silver nitrate solution. 

The precipitate is then dried thoroughly in the water oven, 
separated as completely as possible from the filter, and ignited in 
a platinum crucible tightly covered. Care must be taken to have 
the precipitate thoroughly dry before igniting, and to keep the 
crucible tightly covered until the substance is raised to a full red 
heat. The crucible is then allowed to cool, and the filter added, 
folded up, and again ignited — first with the cover on until all 
inflammable vapors cease to appear, and then with access of air 
until the carbon of the filter is entirely consumed. It is then 
cooled in the desiccator and weighed covered. The weight of the 
precipitate gives the weight of the alumina, A1 2 3 , and sesqui- 
oxide of iron, Fe 2 3 , in 1 gramme of the sample. 

To obtain the amount of alumina, the iron oxide must be sepa- 
rately determined, and its amount deducted from the total weight 
of precipitate, Al 2 3 + Fe 2 3 , as found above. 

To find the amount of iron oxide present, we may take 100 c.c. 
of the original solution above, equal to 5 grammes of the sample. 
This is transferred to a flask holding 200 or 300 c.c, and fitted 
with what is known as a Bunsen or Krooning valve. This con- 
sists merely of a rubber stopper for the neck of the flask, through 
the centre of which is slipped a short piece of glass tubing extend- 
ing just through the stopper below and about one inch above the 
stopper. 

To the upper end is fitted a short piece of rubber tube about 
an inch in length, which has had a short slit cut in one side with 
a sharp knife, the upper end of the rubber tube being stopped 
with a bit of glass rod. This valve will open to relieve a pressure 
from within the flask, but will not admit air into the flask. Some 
pieces of pure iron-free zinc are added to the solution in the flask, 
and enough sulphuric acid to cause a moderately rapid evolution 
of gas. 

The stopper fitted with the valve as above is then inserted, and 
the whole allowed to rest for an hour or two, taking care to keep 
up the evolution of gas during the time by the addition of zinc 



378 THE CHEMISTRY OF PAPER-MAKING. 

or acid as may be needed. The solution is then transferred to a 
large beaker and the flask rinsed in, taking care not to leave 
any undissolved bits of zinc behind. 

A solution of permanganate of potash is then dropped in from 
a burette drop by drop, with constant stirring, until a faint pink 
tint remains in the solution. The number of cubic centimetres of 
permanganate solution used is then read off, and the equivalent 
amount of sesquioxide of iron, Fe 2 3 , ascertained by multiplying 
by the appropriate factor. 

The permanganate solution is made of appropriate strength by 
weighing about 3 grammes of the crystallized permanganate of 
potash and dissolving in water to make 1000 c.c. 

To obtain the value of this solution in terms of iron, Fe, we 
may dissolve about 0.200 grammes of fine piano wire by warming 
with a mixture of 3 volumes of water and 1 volume of sulphuric 
acid in a small flask fitted with a Krooning valve, as described 
above. 

When all is dissolved except some bits of carbon, the whole is 

transferred to a large beaker with 500 to 600 c.c. of water and 

titrated with the permanganate solution as above, until a pink color 

remains. Piano wire we may take as containing 99.7 per cent. 

of iron, Fe. Then, if we have dissolved 0.200 grammes, we shall 

in reality have a solution of (0.200x0.997 = 0.1994) 0.1991 

grammes of iron. Suppose this to have consumed, or decolorized, 

20 c.c. of permanganate solution. Then 1 c.c. of permanganate 

1994 
will be equivalent to ' — = 0.00997 grammes of iron, Fe, or 

0.014243 grammes of Fe 2 O g . 

2Fe Fe 2 3 Fe Fe 2 O s 

112 : 160 = 0.00997 : 0.014243. 

The value of the permanganate solution must be determined each 
time directly before using, as it is apt to lose strength by keeping, 
with the formation of a brown precipitate. The solution of iron 
should always be tested before titrating by removing a small drop 
from the flask by means of a rod and bringing it in contact with a 
drop of a solution of potassium sulphocyanide, placed on a white 
surface, as a porcelain dish. If any reddish color appears at once, 
the iron has not all been dissolved to proto-sulphate, as is necessary 
before it can be titrated. The remedy is simply to allow it to 



SULPHATES. 379 



remain longer in contact with zinc in the act of evolving hydro- 
gen. When the reduction from the ferric to the ferrous condition 
is complete, the solution will give no red color with sulphocyanide 
solution. Certain "patent" or "concentrated" alums are met 
with, which contain a small percentage of zinc sulphate. This 
is formed from the use, at a certain stage of the manufacture, 
of zinc for the double purpose of neutralizing free acid and of 
rendering the alum more porous and consequently more easily 
dissolved. 

A qualitative test for the presence of zinc may be made by 
adding an excess of ammonia solution to a moderately concentrated 
solution of the alum, heating to boiling and filtering from the 
alumina (and iron oxide) precipitated. The clear filtrate is then 
heated to boiling and a little ammonia sulphide solution added. 
If zinc is present, it will appear as a white flocculent precipitate, 
which on boiling for a few moments will readily settle. 

When zinc is present in an alum, the iron may be determined as 
above ; but for the estimation of alumina we must precipitate it 
along with the iron present as basic acetate of the sesquioxide, 
instead of the hydrate as in the former case. 

To this end the solution must be largely diluted — about 1 
gramme of alum in 500 c.c. is proper. To the solution about 2 
grammes of acetate of soda are added, and a few drops of acetic 
acid. The solution is then heated to boiling and kept in active 
ebullition for ten to fifteen minutes. By this means all the 
alumina and sesquioxide of iron are precipitated as basic acetates, 
while the zinc remains in solution. The precipitate is allowed to 
settle, and the liquid decanted through a filter as rapidly as 
possible. The precipitate is boiled up with water two or three 
times, allowed to settle, and the liquid decanted each time ; and 
finally, the precipitate is thrown on the filter and the washing com- 
pleted with boiling water, best containing a very little ammonium 
acetate. The filtrate and washings are to be evaporated to a 
moderate volume — say to about 200 c.c; and if any precipi- 
tate separates during the concentration, as will usually be the 
case, it is to be filtered off, washed, ignited, and weighed with the 
main basic acetate precipitate. 

The alumina precipitate is to be dried and ignited as above, 
and weighed as Al 2 3 + Fe 2 3 . From this weight the weight of 
the Fe 2 3 found by titration with permanganate as above is to be 



380 THE CHEMISTRY OF PAPER-MAKING. 

deducted, and the remainder will be the alumina present in the 
1 gramme of alum taken. 

The filtrate from the basic acetates of alumina and sesquioxide 
of iron is to be neutralized as nearly as possible with ammonia, 
heated to boiling, and ammonium sulphide added drop by drop so 
long as it continues to produce a precipitate. The boiling is to 
be continued for about fifteen or twenty minutes. The zinc sul- 
phide is then allowed to settle, which it will do very rapidly. 
The clear liquor should then be tested with a single drop of 
ammonium sulphide. If this produces no cloud, the liquid may 
be filtered and the precipitate washed thoroughly with hot water. 

If the addition of a drop of the reagent produces a precipitate, 
the liquid should be again boiled and tested, and so on until the 
reagent fails to give any further cloud in the solution. 

The zinc sulphide is to be dried, removed as far as possible 
from the filter into a porcelain crucible, the filter added, and 
ignited with free access of air, gently at first, and finally as 
strongly as possible, with the addition now and then of a small 
piece of ammonium carbonate. The ignition should be continued 
until on cooling and weighing two consecutive weights are 
obtained alike. The strong ignition changes the zinc sulphide 
into zinc oxide, ZnO, and it is weighed as such. 

In the foregoing we have constantly used the word " alum," but 
have really been describing the analysis or valuation of alum 
cake. The methods for the technical valuation of each is the 
same, however, so that a single description may serve for the 
whole class of sulphates commercially known as alums. 

Free Acid in Alum. 

Numerous methods have been proposed for the determination of 
free acid in alums, but after giving them an extended trial in our 
laboratory we have failed to find one which we can accept as even 
fairly accurate. Where this important point must be determined, 
we can, therefore, only recommend a complete analysis. 

Sizing Test. 

- One of the most satisfactory tests to which an alum for paper- 
makers' use can be subjected is that which we have worked out 
and called the " sizing test," by which the actual amount of rosin 



SULPHATES. 381 



size which a given amount of alum will precipitate is determined. 
This is effected as follows. 

A standard size solution is prepared by dissolving about 25 
grammes of good ordinary rosin size in about 250 c.c. of strong 
alcohol. The solution is then filtered from insoluble matter, 
and diluted with a mixture of 500 c.c. of strong alcohol and 
300 c.c. of water to nearly 1000 c.c. A little phenolphtalein 
solution is then added, and standard soda solution added drop 
by drop, shaking after each addition until a faint pink tinge is 
observed in the solution. This shows that all the rosin acids are 
combined with soda, and that the solution is one of neutral 
resinate of soda or neutral rosin size. The solution is now to 
be made to 1000 c.c. with the diluted alcohol mentioned above, 
and if not entirely clear, filtered again or allowed to stand until it 
settles clear. The clear alcoholic solution constitutes the standard 
size solution. 

The value of this solution is next to be determined, best by 
means of a solution of pure crystallized ammonia alum, one part 
of which alum we have found to precipitate 2.46 parts of neutral 
rosin size. 

For this purpose the clear, colorless crystals should be coarsely 
crushed in a mortar, and the resulting powder pressed between 
two sheets of filtering paper to remove any accidental moisture. 
Five grammes are then carefully weighed and dissolved to 500 
c.c. Each cubic centimetre of this solution will then contain 
0.01 gramme of alum. 

Two burettes are next filled, one with the size solution, and one 
with the alum solution. 

A flask of 150 to 200 c.c. capacity is filled about two-thirds 
full of water, and 20 c.c. of the size solution is run into it 
from the burette. The alum solution is next run in, a few drops 
at a time, the mouth of the flask being closed with the thumb and 
the flask vigorously shaken after each addition of alum, and allowed 
to rest until the flocculent precipitate formed has risen clear, 
which takes but a few moments. The addition of the alum solu- 
tion should be continued until the precipitate on rising leaves 
the solution entirely clear, without the slightest trace of milkiness 
or opalescence. 

The number of cubic centimetres of alum x 0.01 equals the 
amount of ammonia alum required to precipitate the size in the 



382 THE CHEMISTRY OF PAPER-MAKING. 

20 c.c. of standard size employed. This multiplied by the factor 
for ammonia alum, as above, equals the quantity in grammes of 
neutral size in 20 c.c. of the standard solution. 

The actual test of an alum is performed in exactly the same 
way ; a solution of 5 grammes of the alum to 500 c.c. being em- 
ployed, and, if necessary, filtered through a dry filter before titrat- 
ing. 20 c.c. of the standard size solution are always employed, 
and the actual amount of neutral size it contains having been 
determined as above, it is easy to calculate from the data given 
by the titration the amount of size which one part of the alum 
tested will precipitate. 

This test, as is evident, gives the absolute precipitating power 
of the alum, and does not discriminate between sulphates of 
alumina, iron, or other metallic oxides which may be present, or 
free acid, all of which have the power of precipitating size. 

Moisture in Alum. 

One other test as applied to alum should, however, be noticed 
before leaving the subject, and that is the determination of 
moisture. This, in the case of alums, cannot be determined, as 
in most instances, by drying or igniting a sample, and noting the 
loss which it sustains. Mere drying, even at a temperature consider- 
ably above 100° C, is not sufficient to expel all the moisture from 
an alum, while ignition drives off not only the water, but a portion 
of the sulphuric acid as well. To determine the moisture in this 
case, then, it is necessary that we ignite the sample, best in a 
platinum crucible, until fumes of S0 3 appear in abundance ; then 
cool and weigh, and note the loss. We next treat the ignited 
sample with hot hydrochloric acid, until all lumps are broken 
down. If the ignition has not been too intense or prolonged, all 
will dissolve. It does not matter, however, if all does not dis- 
solve, provided it is well broken down, so as to make sure that all 
soluble portions are brought into solution. The solution is filtered 
and the residue well washed on the filter with hot water. The 
filtrate and washings are next precipitated with barium chlo- 
ride, and the sulphuric acid determined. The per cent, of S0 3 , 
here found, deducted from the total SO g contained in the 
sample, as determined above (see Sulphate in Soda-Ash), leaves 
the percentage of S0 3 driven off by the ignition. This taken 



SULPHATES. 383 



from the total loss of weight by ignition, in per cents., leaves the 
percentage of moisture in the sample. 



Pearl Hardening (Crystallized Sulphate of Lime). 
Symbol, CaS0 4 , 2 aq. — Molecular weight, 172. 

Pearl hardening being made ordinarily by precipitating a soluble 
salt of lime as calcium chloride by means of sulphuric acid or 
sulphate of soda, washing and pressing in a filter press, the only 
tests which the substance calls for are tests for free acids, for 
chlorides, and for moisture. 

Free acids may be recognized by mixing a portion of the sample 
with water and filtering. If no free acid is present, the filtered 
solution, when tested with litmus solution, should show no acid 
reaction. A portion of the filtered solution just mentioned may 
be tested for chlorides, by adding a drop only of nitric acid and 
some nitrate of silver solution. A slight cloud will usually be 
obtained, as it is difficult to remove all traces of chloride ; but if 
any considerable precipitate forms, it will indicate that the pearl 
hardening has been incompletely washed. 

Moisture may be determined by drying a sample at 100° C. in 
the water-oven until it ceases to lose weight. The total loss 
is equal to the moisture in the sample plus three-quarters of its 
water of crystallization. The remaining water of crystallization 
(one-quarter) can only be driven off at a heat approaching red- 
ness. 

To obtain from these data the actual amount of moisture present 
in the sample apart from the combined water or water of crystal- 
lization, we must make the following calculation. 

The molecular weight of anhydrous sulphate of lime, CaS0 4 , 
is 136. Molecular weight of the crystallized salt, CaS0 4 , 2 aq. 
= 172. Molecular weight of the salt dried at 100° C, CaS0 4 , 

4 

From these figures we may form the proportion as 145, the 
molecular weight of the dried salt, is to 172, the molecular weight 
of the crystallized salt, so is (x), the weight of the dried sample 
to (y~), the equivalent weight of crystallized salt actually present 
in the original sample. This weight (#) deducted from the original 



384 THE CHEMISTRY OF PAPER-MAKING. 

weight of the sample will leave the actual amount of moisture 
or water other than combined water which was expelled from the 
sample at 100° C. 

Sulphate of Magnesia {Epsom Salts'). 
Symbol, MgS0 4 , 7 aq. — Molecular weight, 246. 

The only test called for by this substance is for the presence of 
metals, iron, and lime. 

The former test may be made by slightly acidifying a solution 
of the salt with HC1 and passing sulphuretted hydrogen gas 
through the solution. The formation of a colored precipitate 
indicates the presence of some of the heavy metals. The solution 
may be tested for iron sesquioxide by potassium ferrocyanide or 
sulphocyanide (see Testing Alum for Iron above). 

If the sample is well crystallized and does not present a white, 
floury appearance, the presence of sulphate of lime in much more 
than traces can hardly be expected. 

The solution may be tested for lime, however, by adding enough 
ammonium chloride solution to prevent the formation of a pre- 
cipitate by ammonia. The latter is then added in excess and a 
little ammonia oxalate solution. The almost immediate formation 
of a fine white precipitate indicates the presence of lime. 

Sulphate of Zinc (White Vitriol). 

Symbol, ZnS0 4 , 7 aq. — Molecular weight, 287. 

Sulphate of iron is a common impurity in this salt and may be 
tested for as under Sulphate of Magnesia, which see, and the amount 
of iron oxide, F 2 3 , may be determined if desired, by precipitation, 
with excess of ammonia, and igniting the precipitate after careful 
washing and weighing as Fe 2 3 . 

Sulphate of Copper (Blue Vitriol — Blue Stone). 
Symbol, CuS0 4 , 5 aq. — Molecular weight, 249.4. 

The "blue stone " of commerce almost always contains more or 
less sulphate of iron. This may be recognized by adding to a 
solution of the salt, ammonia sufficient to redissolve the precipitate 



SULPHATES. 385 

of cupric hydrate first formed to form a clear, deep blue solution. 
The solution is then filtered, when any sesquioxide of iron present 
will remain on the filter, and may after washing be recognized by 
the appropriate tests. 

The iron sulphate may nearly all be removed by dissolving the 
" blue stone " in hot water and recrystallizing. 

Sulphate of Iron (Copperas — Green Vitriol'). 

Symbol, FeS0 4 , 7 aq. — Molecular weight, 278. 

The only test of this salt likely to be of use in a paper mill is a 
determination of the amount of bleaching-powder solution required 
to oxidize or rust a given amount. For this purpose a solution of 
the sulphate of iron is prepared containing 25 grammes to 1000 
c.c. 100 c.c. of this solution, equal to 5 grammes of the sample, 
are diluted to at least 500 c.c. in a large beaker, and acidified 
strongly with sulphuric acid. The bleach solution it is proposed 
to use for "rusting" the "copperas" is then dropped in from 
a burette, with constant stirring, until a drop of the iron solution 
removed on a rod no longer gives a blue color when mixed on a 
porcelain plate with a drop of weak, freshly prepared solution of 
ferrocyanide of potassium. The number of cubic centimetres of 
bleach solution used is the measure of the amount of this solution 
required to oxidize or " rust " 5 grammes of the copperas. This 
process does not give strictly accurate results, but a sufficiently 
close approximation for practical work. 

Salt Cake. 

This is a residue left from the treating of common salt with 
sulphuric acid in the manufacture of muriatic acid, and consists 
for the most part of bisulphate of soda with varying amounts of 
neutral sulphate and chloride of sodium. 

It is often of value to know the amount of free acid in the 
sample. By free acid in this connection is meant not only that 
which is actually free and uncombined with any base, but also 
that which is in excess of the amount required to form neutral 
sodium sulphate, Na 2 S0 4 , and which is, we may say, loosely com- 
bined as sodium bisulphate, NaHS0 4 . This may be . determined 
by titrating a solution of the salt directly with standard soda 



386 THE CHEMISTRY OF PAPER-MAKING. 

solution, as previously described (see Determination of Strength of 
Sulphuric Acid). For technical purposes it is rarely necessary to 
determine bases, other than soda present, in salt cake, as their 
amount is usually slight. 

The total amount of neutral sulphate of soda, equivalent to the 
total base present, may be readily determined by adding a slight 
excess of ammonia to a solution of about 1 gramme of the 
substance, heating till the smell of ammonia can no longer be 
perceived, and filtering from any precipitate of alumina and iron 
oxides, which may, after washing, be ignited, and their weight de- 
termined if desired, and evaporating the nitrate and washings to 
dryness in a platinum dish over the water-bath. When thoroughly 
dry, the residue should be ignited, cautiously at first, and finally to 
redness. After cooling it should be moistened with dilute ammonia 
and again dried and ignited, cooled in a desiccator, and weighed as 
neutral sulphate of soda, Na 2 S0 4 . 

CHLORIDES (MURIATES). 

Chloride of Sodium (Common Salt). 

Symbol, NaCl. — Molecular weight, 58.5. 

For specific gravity of solutions and per cent, of NaCl contained, see Appendix. 

Common salt usually contains, as impurities, small amounts of 
sulphate of lime and chloride (or sulphate) of magnesia, and 
frequently traces of salts of iron and alumina. 

The method of analysis of sodium chloride will serve in the 
main for all the commonly occurring chlorides. For the determi- 
nation of the small amounts of impurities, a convenient quantity 
to weigh out is 20 grammes. This is dissolved in about 200 c.c. 
of water and acidified with a few drops of hydrochloric acid. 
The solution, filtered if necessary from any insoluble matter, is 
rendered alkaline by the addition of ammonia in slight excess, 
and heated to near boiling until all odor of ammonia has dis- 
appeared, the volume of the solution being maintained by the 
addition of hot distilled water from time to time as required. The 
solution is filtered from the alumina and sesquioxide of iron pre- 
cipitated, and the precipitate well washed, dried, ignited, and 
weighed. The lime is separated from the filtrate from the last 
precipitate by the addition of ammonia oxalate solution. This 



CHLORIDES. 387 



should be added to the hot liquid, and after boiling, the whole 
allowed to stand in a warm place until the precipitate has settled. 
It is then filtered and the precipitated oxalate of lime washed with 
hot water, dried, and ignited as strongly as possible for a quarter- 
to a half-hour or longer if the precipitate is in any considerable 
amount. It is well to guard against error at this point by igniting 
and weighing a second time, and repeating until two consecutive 
weights are obtained which are identical. The strong ignition 
changes the oxalate of lime into lime or calcium oxide, CaO, 
which is the substance weighed. 

The filtrate from the oxalate of lime precipitate is rendered 
strongly alkaline by ammonia, and some phosphate of soda solu- 
tion added, and after stirring, allowed to stand for some hours to 
separate magnesia as the double phosphate of ammonia and mag- 
nesia. This precipitate, filtered out and washed with a solution 
of ammonia (1^ volumes of strong ammonia to 8 1 - volumes of 
water), is dried and ignited strongly, and weighed as magnesium 
pyrophosphate, which multiplied by 0.3604 gives the equivalent 
magnesia, MgO. 

This completes the estimation of bases necessary. 

Sulphuric acid is determined in a solution of 20 grammes acidified 
with hydrochloric acid, and filtered, if necessary, by precipitation 
with barium chloride (compare estimation of S0 3 in Soda-Ash). 

For the determination of chlorine, 10 grammes of the sample 
are weighed and dissolved to 1000 c.c. 

100 c.c. of this solution, containing 1 gramme of the sample, 
are diluted to 500 c.c. and 50 c.c. of the latter solution, equivalent 
to 0.1000 gramme of the sample, are taken for the test. This is 
placed in a beaker, and a small bit of neutral potassium chro- 
mate about the size of a pin-head added and dissolved, which 
should color the solution a light yellow. A ^-normal solution of 
silver nitrate (prepared as below) is then dropped in from a 
burette (one with glass cock should be employed), with constant 
shaking or stirring. Each drop as it falls into the salt solution 
produces a brick-red spot of silver chromate, which, so long as 
any chlorine remains in the solution, disappears at once on 
stirring, being changed into white silver chloride. So soon, 
however, as all the chlorine present has been converted into silver 
chloride, the red silver chromate remains permanent, and a single 
drop of the silver nitrate solution is sufficient to give a perceptible 



388 THE CHEMISTRY OF PAPER-MAKING. 

reddish tinge to the solution, and this is the end reaction. The 
cubic centimetres of silver solution used are then read off, and this 
number multiplied by 0.00355 gives the equivalent weight of 
chlorine, or by 0.00585 the equivalent weight of salt, NaCl, in 
substance taken (0.1000 gramme) for the titration. 

The -^normal silver nitrate solution may be prepared with 
accuracy by weighing 16.966 grammes of pure silver nitrate and 
dissolving in distilled water to make 1000 c.c. 

The silver nitrate should be very cautiously fused over a low 
flame in a porcelain crucible, employing only just sufficient heat to 
effect the fusion, since a high heat might decompose a portion of 
the salt. The mass after cooling should be coarsely powdered in a 
clean porcelain mortar, and the above-named weight of the powder 
taken to make the solution. Only pure distilled water must be 
used, since other water almost always contains either chlorides or 
organic matter, either of which would precipitate a portion of 
the silver, and consequently the solution would not be stuictly 
^-normal. 

The value of the solution may be tested, and if not strictly 
-J^-normal, a factor for its reduction to the latter may be found 
by titrating a weighed amount of pure NaCl with it in the same 
way as described above. 

Pure salt may be readily prepared by evaporating a filtered solu- 
tion of ordinary salt over the water-bath until only a small amount 
of liquid remains. 

This is drained from the crystals of salt while hot, the crystals 
quickly rinsed with a little distilled water, and redissolved in 
distilled water, and the process repeated at least three times 
in all. The crystals are then dried at 100° C. and preserved for 
use. 

To test the standard silver solution, a portion of the chemically 
pure salt should be powdered, and the powder heated nearly to 
redness to expel any moisture, and transferred while quite warm 
to a light bottle or tube having a well-fitting glass stopper. After 
tube and contents are entirely cold they are weighed, about 100 
grammes are shaken into a beaker, and tube and contents weighed 
again. The difference between the first and second weights gives 
the amount taken for the titration. Suppose we have taken 0.095 
grammes of salt and find that it takes 17.2 c.c. of the silver 
solution to give a perceptible red color to the solution (colored 



CHLORIDES. 389 



with chromate of potash). Then the value of our solution will be 
)5 = 0.0055232 N ) 0.0055232 grammes, NaCl, per cubic centi- 



17.2 

metre ; or if we wish a factor to reduce our solution to -^normal 
cubic centimetres, we may find it by the proportion, 

0.00585 : 0.0055232 = 1 : x, the required factor. 

For the estimation of chlorine by titration with standard silver 
solution, as above, it is necessary always that the solution be 
neutral in reaction. An acid solution may be rendered neutral by 
digestion for some time with powdered Iceland spar, which is pure 
calcium carbonate. An excess of the powder does not interfere in 
any way with the titration so that it need not be filtered out. In 
some cases it is preferable to precipitate the chlorine with an excess 
of silver nitrate and to weigh the silver chloride after gently 
igniting. For this purpose the solution of the chloride should not 
be too dilute, and should be slightly acidulated with nitric acid. 
The solution should be heated and the silver solution (quite 
strong) added in excess and the solution vigorously stirred. It 
should then be allowed to stand in the dark until the silver chlo- 
ride has settled clear. It is then thrown on a filter and washed 
as rapidly as possible with hot water thoroughly. It is then dried, 
removed as thoroughly as possible from the filter to a small, 
weighed porcelain crucible, the filter burned separately, and the 
ash added to the silver chloride in the crucible. The whole is 
next moistened with a drop of nitric acid and warmed gently. A 
drop of HC1 is then added and the crucible cautiously warmed 
with a low flame until the silver chloride begins to melt. It is 
then cooled and weighed. The weight of chloride of silver, 
AgCl, found multiplied by 0.2489 = chlorine, CI, or multiplied by 
0.40863 = chloride of sodium, NaCl. 

Magnesium Chloride. 
Symbol, MgCl 2 . — Molecular weight, 95. 

Crystallized Magnesium Chloride. 

Symbol, MgCL, , aq. 

This salt is of interest to the paper-maker mainly on account of 
its being the material employed in the Hermite electric bleaching 
process. It usually contains a little calcium chloride, CaCl 2 , and 



390 THE CHEMISTRY OF PAPER-MAKING. 

frequently a little sodium chloride. These, however, do not unfit 
it for the above purpose. The only tests necessary for this sub- 
stance are a determination of total chlorine, insoluble matter, and 
moisture. 

The first may be determined by titration with standard silver 
solution, in the filtered solution as described, under Sodium 
Chloride. 

The insoluble matter is determined by simply filtering out from 
the aqueous solution and weighing after ignition. 

The determination of moisture in this substance is somewhat 
difficult, since the salt does not part with all its water at 100° C, 
and on ignition it loses beside the water a portion of its chlorine. 
A method which is perhaps the simplest of all, and sufficiently 
accurate for technical purposes, is to first determine the total 
chlorine in a portion of the sample. A second portion is to be 
quite strongly ignited in a porcelain crucible and weighed after 
cooling. The loss will be the water together with more or less of 
the chlorine. The ignited sample is next boiled with water and 
filtered and the chlorine determined in the filtrate. The difference 
between the chlorine found in this and the original sample will 
represent the amount of chlorine which was expelled by ignition. 
This deducted from the total loss of the sample by ignition leaves 
the water in the sample. 

Calcium Chloride. 
Symbol, CaCl 2 . — Molecular weight, 111. 

This salt is rarely or never seen at present in a paper mill, 
but as it has also been proposed for use in electric bleaching, we 
note it here. It has a very great affinity for water, so great that a 
lump of the solid substance left exposed to the air will in a few 
hours attract so much moisture from the air as to liquefy itself. 

Tests for free acid, total chlorine, insoluble matter, and moisture 
are required by this substance. 

Free acid may be detected by means of litmus solution, and, if 
present, may be directly titrated with standard soda. 

Total chlorine is determined exactly as in the case of sodium 
chloride. In the absence of free acid, the moisture may be deter- 
mined by the loss on careful ignition to a heat a little below 
redness. If free acid is present, the same procedure must be 



HYPOCHLORITES. 391 

followed as described for the determination of moisture in mag- 
nesium chloride. 

Sesquichloride of Iron. 
Symbol, Fe. 2 Cl 6 . — Molecular weight, 325. 

Solution of sesquichloride of iron, or ferric chloride, is occa- 
sionally employed to give a reddish tinge to paper. The salt 
always has an acid reaction, but in well-prepared samples the 
amount of free acid is slight, and the solution is so sparingly 
employed that it may usually be disregarded. 

It is frequently desirable to know the actual amount of iron 
contained in a solution of this salt or in the commercial article. 
This may be readily determined by reducing a solution of the 
salt with zinc and sulphuric acid and titrating the reduced solu- 
tion, after diluting largely with distilled water, with standard 
permanganate solution. (Compare estimation of iron oxide in 
alum.) 

If it is desired to calculate the actual amount of ferric chloride 
equivalent to the sesquioxide of iron found, it may be done by 
the proportion — 

Fe 2 3 Fe 2 Cl 6 

160 : 325 = Fe 2 3 found : Fe 2 Cl 6 equivalent to same. 

The metal iron equivalent to the sesquioxide found may be 
found by the proportion — 

Fe 2 3 2 Fe 

160 : 112 = Fe 2 3 found : equivalent Fe. 



HYPOCHLORITES. 

Calcium Hypochlorite {Chloride of Lime). 

Symbol, Ca 2 CIO. — Molecular weight, 143. 

Calcium hypochlorite constitutes the valuable ingredient in 
" bleaching-powder," and in a good article is present to the extent 
of from 65 to 75 per cent. The balance of " chloride of lime " 
consists of varying proportions of moisture, calcium hydrate, 
calcium carbonate, calcium chlorate, and calcium chloride. The 
only one of all these substances having any value as a bleaching 
agent in an alkaline solution such as a solution of bleaching- 



392 THE CHEMISTRY OF PAPER-MAKING. 

powder always is, is the calcium hypochlorite. The custom of the 
trade is, however, to reckon the value of bleaching-powder in 
terms of " available chlorine " instead of in terms of actual calcium 
hypochlorite. This " available chlorine " is in fact that portion 
of the total chlorine contained in the sample which is actually in 
combination as an integral part of the bleaching compound, which 
is, as we have said, calcium hypochlorite, and the percentage of 
" available chlorine " is to the equivalent amount of calcium hypo- 
chlorite as 71 is to 143. 

Various methods have been proposed for the determination of 
" available chlorine " in bleaching-powder. The method of sim- 
plest application, and all things considered the most satisfactory 
method for this determination, depends on the fact that hypo- 
chlorous acid, either free or in combination, has the power of 
converting arsenious acid (As 2 3 ) into arsenic acid (As 2 5 ), 
and in doing so it is itself reduced to hydrochloric acid or a 
chloride. 

The carrying out of the process requires a deci-normal solution 
of arsenite of soda, and some starch paste having a small amount 
of potassium iodide dissolved in it. 

The arsenite of soda solution is prepared by weighing roughly 
30 grammes of pure crystallized carbonate of soda or about 12 
grammes of the dry salt, and dissolving it with heat in about 
100 c.c. of distilled water. 

4.95 grammes accurately weighed of chemically pure arsenious 
acid is added to the solution, and the whole heated nearly to boil- 
ing, best in a covered beaker, until the arsenic is entirely dissolved. 
This solution after cooling is to be diluted to exactly 1000 c.c. 
with distilled water, and forms the deci-normal solution of sodium 
arsenite, 1 c.c. of which will be changed to sodium arseniate by, or 
is equivalent to, 0.00355 grammes of active (bleaching or hypo- 
chlorous) chlorine. 

The starch paste is made by adding a very little starch, pre- 
viously rubbed up with a little water, to a considerable amount of 
boiling water, and after cooling, adding a very little potassium 
iodide and stirring well. 

The bleaching-powder to be tested should be well mixed and 
the lumps broken down. 

3.55 grammes are then to be weighed on a glass accurately and 
transferred to a small porcelain mortar, and rubbed to a cream 



HYPOCHLORITES. 393 

quickly with a little water. More water is then added, and well 
stirred with the pestle, allowed to stand for a moment for any 
lumps to settle, and the turbid liquid poured off into a litre flask. 
The residue in the mortar is again ground with water, allowed to 
settle for a moment, and the liquid decanted into the litre flask 
with the former, and the grinding and decanting repeated as long 
as any grains remain in the bottom of the mortar after decanting. 
The mortar and pestle are finally well rinsed and the rinsings 
added to the solution in the flask, which is finally made to the 
1000 c.c. mark and well shaken. 

100 c.c. of the turbid solution is then measured out, without 
filtering or allowing to settle, and transferred to a beaker, and the 
arsenic solution described above run in, slowly and with thorough 
stirring, from a burette. From time to time a drop of the solu- 
tion should be removed from the beaker, by means of the glass 
stirrer, and brought in contact with a drop of the starch paste 
previously placed on a white porcelain surface. So long as a 
trace of hypochlorite remains in the solution, it will produce a 
more or less deep blue color with the iodized starch paste. The 
arsenic solution should be added, drop by drop, when the blue 
color given by a drop of the solution being titrated and a drop of 
the starch begins to fade, and the disappearance of the blue 
altogether marks the end of the reaction. The number of cubic 
centimetres of the arsenic used reads directly the percentage of 
available chlorine in the sample when the above weights and 
measures are adhered to. 

In Europe it is customary to employ an acid solution of arsenic, 
made by dissolving the arsenious acid in hydrochloric acid and 
diluting, instead of in carbonate of soda, as above. The results 
obtained by the use of this solution are, however, apt to be too 
high, since the chlorate present acts in an acid solution to oxidize 
the arsenious acid in the same way as the hypochlorite, while the 
former is entirely without action on the arsenic so long as the 
solution remains alkaline. 

The use of alkaline arsenic also corresponds more nearly to the 
conditions of practice in the use of bleaching-powder solutions, 
where the oxidizing or bleaching action takes place in strongly 
alkaline solutions. 



394 THE CHEMISTRY OF PAPER-MAKING. 

Magnesium Hypochlorite. 
Symbol, Mg 2 CIO. —Molecular weight, 127. 

Magnesium hypochlorite is only known in solution and is 
chiefly interesting as being the bleaching agent in the Hermite 
electric bleaching process. It is the main product of the elec- 
trolysis of a solution of magnesium chloride under the conditions 
of this process. The strength of a solution of magnesium hypo- 
chlorite is measured in terms of available chlorine or active 
chlorine, as in the case of ordinary bleaching-powder solution and 
is determined in precisely the same way. 

Potassium Hypochlorite. 
Symbol, KCIO. —Molecular weight, 90.6. 

Sodium Hypochlorite. 
Symbol, NaClO. — Molecular weight, 74.5. 

Both these hypochlorites are known only in solution, and are 
made by decomposing a solution of hypochlorite of calcium by 
equivalent quantities of carbonate of potassium or sodium. The 
former is known in pharmacy as Javelle water, or " Eau de 
Javelle," and is chiefly employed for medicinal purposes. 

Solution of hypochlorite of sodium is the "chlorinated soda" of 
the shops, and is also known as Labarraque's disinfectant solution. 
All the hypochlorite solutions possess bleaching and disinfecting 
properties, dependent upon the hypochlorous, or active, chlorine 
present. The strength of all is expressed in terms of available 
chlorine and is determined by titration with deci-normal solution 
of arsenite of soda, as described under Hypochlorite of Calcium. 

In testing solutions of hypochlorites, it is convenient to weigh 
out the number of grammes of the solution corresponding to the 
molecular weight of chlorine (35.5 grammes) and make up to 
1000 c.c. 

100 c.c. of this solution is measured and made again to 1000 c.c, 
and 100 c.c. of this second solution is taken up for the titration. 
The number of centimetres of deci-normal arsenic solution con- 
sumed will then indicate directly the per cents, of active chlorine 
in the original solution without any calculation. 



NITRATES. 395 



ANTICHLORS. 

Antichlors are of two kinds: The first, or antichlors proper, 
oppose the action of hypochlorous acid, either free or combined, 
by abstracting its oxygen and thus leaving the chlorine in the 
form of hydrochloric acid (or a chloride), whose chlorine is 
inactive. 

This class is found in the lower oxides of sulphur, as sodium 
hyposulphite (or thiosulphate), Na 2 S 2 3 , and sulphurous acid 
(S0 2 ) and its compounds, the sulphites and bisulphites. 

These all serve to break up the hypochlorous compound as 
indicated above. They are all to be tested for their antichlorine 
strength, if we may be allowed the use of the term, by means of a 
deci-normal solution of iodine, the preparation and use of which 
will be explained under Analysis of Bisulphite Solutions below, 
which see. 

The strength of an antichlor is conveniently expressed in terms 
of the chlorine which it will serve to "kill," reckoned in per 
cents, on the antichlor tested. 1 c.c. of deci-normal iodine solu- 
tion is equivalent to 0.00355 grammes of active chlorine in this 
sense. 

The second class of antichlors consists of substances which are 
capable of absorbing oxygen or chlorine, as the case may be, 
from the hypochlorous compound, and of combining directly with 
it. 

To this class belong turpentine and essential oils in general 
which absorb oxygen directly. The caustic alkalis and ammonia 
are also antichlors to a degree, and act by combining directly with 
chlorine to produce chlorides. 

NITRATES. 

Nitrate of Potash (Saltpetre'). 
Symbol, KN0 3 . — Molecular weight, 101.1. 

The impurities in commercial saltpetre are small amounts of 
chloride of sodium and sulphate of potash, a little moisture, and 
organic matter. 

The chloride of sodium is calculated from the chlorine found 
by titrating a solution of 10 grammes of the salt with standard 



396 THE CHEMISTRY OF PAPER-MAKING. 

silver nitrate solution. (Compare determination of chlorine in 
Chloride of Sodium — common salt.) 

Cl NaCl 

35.5 : 58.5 = chlorine found : equivalent sodium chloride. 

Sulphate of potash is calculated from the sulphuric acid (S0 3 ) 
found by precipitating a solution of 10 grammes of the nitrate, 
acidified with a few drops of hydrochloric acid, with barium 
chloride. (Compare Determination of Sulphuric Acid in Soda Ash.) 
The proportion is — 

S0 3 K,S0 4 

80 : 174.2 = S0 3 found : equivalent sulphate of potash. 

The moisture and organic matter are determined from the loss 
on cautiously fusing 10 grammes of the sample in a porcelain 
crucible, covered, over a very low flame. As soon as the mass is 
completely fused, the heat should be removed, and the whole 
allowed to cool ; and when completely cold, it is to be weighed. 
It is convenient to first weigh the crucible and cover, and then 
weigh into it 10 grammes of the nitrate for the fusion. 

The actual KN0 3 is determined by difference between the per- 
centage of the total impurities, determined as above, and 100 per 
cent. 

Crude saltpetre often contains a small amount of nitrate of 
soda, but except in special instances its presence is unimportant,. 

Nitrate of Soda QChili Saltpetre). 

Symbol, NaN0 3 . — Molecular weight, 85. 

What has been said above in regard to nitrate of potash applies 
equally to nitrate of soda, with the exception that in the latter 
salt the small amount of sulphuric acid present is to be considered 
as combined with soda instead of with potash. The formula, 
then, for converting the S0 3 found into equivalent sulphate of 
soda will be 

S0 3 Na,S0 4 

80 : 142 = found : equivalent Na 2 S0 4 . 



ACETATES. 397 



Nitrate of Iron. 
Symbol, Fe 3 N0 3 . — Molecular weight, 242. 

This always occurs in commerce as a solution. 

It is frequently employed for the same purpose as ferric chlo- 
ride (which see), and by dyers is employed in conjunction with 
different forms of tannin solutions in dyeing blacks, and hence is 
frequently called " black liquor." 

The only test called for by this substance is a determination of 
the total iron oxide it contains. For the method compare Sesqui- 
chloride of Iron. 

ACETATES. 

Acetate of Lead (" Sugar of Lead "). 
Symbol, Pb 2 C 2 H 3 2 , 3 aq. — Molecular weight, 379. 

Acetate of lead is almost the only acetate ever employed in 
a paper mill. This is used in conjunction with a bichromate in 
the production of the canary-yellow chromate of lead. The test of 
this substance is for the total amount of soluble lead it contains, 
and this is calculated to the acetate. The method for determining 
the soluble lead present consists in adding to a filtered solution of 
the salt, which should be rather dilute and acidified with a few 
drops of acetic acid, a solution of bichromate of potash in excess. 
The liquid should be well stirred and allowed to stand in a warm 
place until the precipitate has settled, leaving the liquid clear. 
It is then to be filtered through a filter which has been previously 
balanced by means of another filter on the opposite scale-pan. 
The precipitate is well washed with hot water, the washing being 
continued until the washings come off colorless. The filter con- 
taining the precipitate is then dried, together with its companion 
filter, in the water-oven until it ceases to lose weight; and weighed, 
the empty filter being placed on the opposite scale-pan. The 
weight of the chromate of lead weighed, multiplied by 0.68947, 
equals oxide of lead, PbO. The equivalent acetate of lead may be 
found by the proportion — 

PbO Pb 2 C 2 H,0 2) 3 aq. 

222 : 378 = oxide of lead found : equivalent acetate of lead. 



398 THE CHEMISTRY OF PAPER-MAKING. 

CHROMATES. 

Bichromate of Potash. 

Symbol, K 2 Cr 2 7 . — Molecular weight, 295.2. 

Bichromate of potash occurs in so great a state of purity as to 
hardly ever call for a test. If, however, this is desired, the total 
amount of chromic acid, Cr0 3 , may be determined by precipitating 
a solution containing a known amount of the sample by means of 
a solution of pure acetate of lead, acidified with acetic acid, and 
weighing the resultant lead chromate (compare Acetate of Lead). 
Chromate of lead, multiplied by 0.31053, equals chromic acid, Cr0 3 . 

Bichromate of Soda. 

Symbol, Na 2 Cr 2 7 . — Molecular weight, 263. 

This salt is frequently employed for the same purpose as 
bichromate of potash on account of its less cost. It possesses the 
disadvantage, however, of being somewhat deliquescent. The 
proportion of actual chromic acid, Cr0 3 , may be determined as in 
bichromate of potash if desired. Theoretically, 263 parts of this 
salt will precipitate the same amount of lead acetate as 295.2 parts 
of the potassium bichromate. 

MINERAL COLORS. 

Chrome Yellow ( Canary Yellow — Canary Paste) . 

Pure chrome yellow, or neutral chromate of lead, is found when 
solution of bichromate of potash or soda is mixed with a solution 
of a neutral salt of lead, such as the acetate or the nitrate of lead, 
as a bright yellow precipitate. It is entirely insoluble in pure 
water, and only slightly soluble in dilute mineral acids. In 
practice it is often formed in and on the fibre by first impregnating 
the fibre with a solution of sugar of lead in the beating engine, and 
then adding a solution of bichromate. 

It occurs in commerce both as a dry powder and in the form of 
paste. The former is little liable to adulteration, as any addition 
would tend to change the shade of color. 

The canary paste is, however, sometimes falsified by a judicious 
addition of ochre, clay, or barytes, with the aid of one of the 



MINERAL COLORS. 399 



brilliant yellow "aniline," or "azo," colors, or even picric acid. 
Mineral additions may be detected by treating a sample of the 
paste with weak caustic potash solution, which dissolves lead 
chromate to a clear yellow solution, while any of the mineral 
adulterants likely to be present would remain undissolved by the 
potash. 

The presence of "azo" colors may be detected by treating a 
sample of the paste with strong alcohol. If only chromate of 
lead is present, the alcohol will remain colorless, while the other 
yellows will be dissolved and will appear in the alcohol. 

Besides the canary or neutral chromate of lead there are basic 
lead chromates, varying in tint all the way to a brick-red or even 
crimson, some of them even rivalling vermilion in beauty and 
brilliancy. 

Orange Mineral. 

This is a manufactured lead pigment made by roasting the 
carbonate of lead under special conditions as regards temperature 
and access of air to the furnace. 

On boiling with a considerable quantity of moderately dilute 
hydrochloric acid, orange mineral should dissolve without residue 
to a colorless solution. The solution should give no red color 
with potassium sulphocyanide, indicating that oxide of iron is 
absent. 

Venetian Red. 

Venetian red is a nearly pure sesquioxide of iron, and may be 
obtained in quite a variety of shades, the different shades being 
imparted to it by roasting at various temperatures and under 
various other conditions. 

The pigment should be nearly all soluble in strong hydrochloric 
acid on heating with it. The small amount insoluble should be of 
a pure white color after washing. 

The hydrochloric acid solution boiled with excess of ammonia 
and filtered from the ferric hydrate precipitated, should give, 
when tested with ammonium oxalate solution, only a small pre- 
cipitate of oxalate of lime. 

A portion of the hydrochloric acid solution tested with barium 
chloride solution should give but a slight precipitate. 



400 THE CHEMISTRY OF PAPER-MAKING. 



Indian Med. 

This is a mineral of complex composition which owes its color 
to a compound of ferric oxide. It should yield to boiling hydro- 
chloric acid a moderate quantity of sesquioxide of iron. 

Prussian Blue or Berlin Blue. 

This is a ferrocyanide of iron. A pure Prussian blue should be 
odorless, of a bright blue color, with a coppery lustre. It should 
yield nothing to water or to dilute hydrochloric acid. On igni- 
tion, it should smoulder like tinder. The ignited residue should 
be entirely soluble in strong hydrochloric acid by continued heat- 
ing with the same. The solution, after the precipitation of sesqui- 
oxide of iron by the addition of an excess of ammonia, should give 
no precipitate on the addition of ammonium oxalate solution. 

Ultramarine. 

Ultramarine is a peculiar compound of complex composition. 
The color is very sensitive to acids, being rapidly discharged by 
all the mineral acids even when very dilute. This character 
serves to distinguish it from Prussian blue. On the other hand, 
alkalis have no action on this color, while the color of Prussian 
blue is discharged by them. 

An admixture of Prussian blue with ultramarine may be recog- 
nized by treating the sample with a moderately strong solution of 
caustic soda, and filtering. The filtered solution is then acidified 
with hydrochloric acid and a few drops of ferric chloride solution 
added. If Prussian blue were originally present, the addition of 
the ferric chloride will determine the formation of the same color 
in this solution. 

Other Mineral Colors 

of use to the paper-maker are certain colored clays known as 
ochres. These may be obtained of almost any shade from that 
of sienna and Vandyke brown to a cream-white. They all owe 
their color to sesquioxide of iron in varying proportions and com- 
binations. In most instances the iron oxide may be all removed 
by treatment with boiling hydrochloric acid, leaving a pure white 
residual clay. 



ANILINE COLORS. 401 



With these, as with clays proper, the technical test is more 
mechanical than chemical and relates to the fineness of the 
material and its freedom from grit. The presence of grit may be 
detected roughly by rubbing a bit of the sample between the teeth 
when the presence of gritty particles may be felt. 

The character of the grit and its approximate amount may be 
determined by a flotation experiment as follows : — 

A considerable quantity of the material, say 100 grammes, is 
well stirred with a pailful of water, best in a glazed earthenware 
jar. It is then allowed to stand at rest for a few moments, five 
minutes perhaps, for the heavier particles to deposit, and the milky 
portion carefully poured off from the sediment. This is again 
stirred with a fresh portion of water and poured off, and the pro- 
cess continued until the water becomes almost clear in the time 
allotted. 

The sediment remaining is then transferred to a small beaker 
and allowed to deposit, and finally the water is drained off as 
closely as possible and the sediment dried and weighed. It may 
then be examined with a glass or otherwise as desired. If time 
enough is given for depositing each time, this sediment will con- 
tain all the grit of the sample. 

In the matter of clays it is often of advantage, in judging of the 
character of a clay as to its suitableness for use in paper, to have 
a complete analysis of it, since what might pass as clay under an 
ordinary inspection an analysis might prove to be an entirely 
different substance and one which might not be well retained in 
the paper, or if retained might give an undesirable harshness or 
other quality to the sheet. 

An analysis of this kind would, however, necessarily be made 
by a professional chemist. 

All the mineral colors and clays are insoluble in water, and in 
the paper remain on the surface of and between the fibres of the 
sheet. 

ANILINE COLORS. 

The " aniline colors," on the other hand, as well as carmine, are 
all soluble colors and penetrate the fibre. The only test to be 
applied to these colors is one which has in view to determine 
comparatively the intensity of the tinctorial power, or, in other 



402 THE CHEMISTRY OF PAPER-MAKING. 

words, the comparative strength of different samples relatively to 
their cost. 

This is known as the "money-value test." 

In applying this test, we do not weigh equal amounts of each 
sample if their price per pound is different, but that amount of 
each which the same amount of money will buy for the several 
amounts to be taken for the test. For example, if we wish to 
compare three different samples of soluble blue costing, say 
16 cents, 20 cents, and 23|- cents respectively, we would weigh 1.6 
grammes of the first, |4 of 1.6 grammes = 1.28 grammes of the 

second, and — — of 1.6 grammes = 1.0893 grammes of the third, 

and dilute the solution of each of these amounts to 1000 c.c. 

A convenient amount (say 10 or 20 c.c.) of the solution made 
from the lowest priced sample is next placed in a tall narrow 
bottle, or jar of clear glass, and diluted to a rather light tint with 
water, noting the amount of water added. The same amount of 
each of the other solutions is then measured and diluted in similar 
bottles or jars, until the depth of the tint of the solutions matches 
that of the first solution diluted, and the volume of the water 
required noted in each case. Then suppose we have diluted our 
first sample to 100 c.c, 10 c.c. of the strong solution being taken ; 
the second requires 86 c.c. of water to match the shade, making 
96 c.c. in this ; and the third requires 120 c.c. — making 130 c.c. 
in all. 

Then the tinctorial values of the three samples will be as 100, 
96, and 130 per unit of cost, while their cost per unit of weight 
was as 16, 20, and 23^, respectively. Graphically expressed, the 
result of the test we have cited would be : — 

1 lb. @ 16 cts. will color to a given shade 100 lbs. of pulp, 
0.8 lb. @ 20 cts. will color to a given shade 96 lbs. of pulp, 
0.68 lb. @ 23^ cts. will color to a given shade 130 lbs. of pulp ; 

and conversely, to color 100 lbs. of pulp to a given shade will 
require of 

Sample 1, @ 16 cts., 1 lb., costing 16 cts. 

Sample 2, @ 20 cts., 0.833 lb., costing 16f cts. 

Sample 3, @ 231 cts., 0.523 lb., costing 12| cts. 

showing that in the case we have taken for example the best is 
the cheapest to use, while that costing the lowest price per pound 



WATER ANALYSIS. 403 



stands second in the list, and the sample at the medium price 
proves to be the most expensive of the three. 

This method of " money-value testing " is largely adopted by 
dealers in dyes and extracts; and while not giving absolute values 
in per cents, of actual color present, it furnishes comparisons 
which could hardly be arrived at in any other way and which are 
often of much value. 

WATER ANALYSIS. 

No single element in the location of a paper mill is deserving of 
more consideration than that of the water supply. Not only for 
use in steam-generating boilers, but for the other purposes of the 
paper-maker, an abundant supply of water of good quality is of 
the highest importance. 

The only means of judging beforehand of the character of a 
water lies in a more or less complete chemical examination. The 
color, smell, and taste of a water are, as far as they go, indications 
of its probable character, but it must be borne in mind that a 
water having the characteristics of good color, taste, and smell 
may be heavily charged with very troublesome mineral matters, 
while, on the other hand, one in which these characteristics are 
had, may still contain little which will interfere with the opera- 
tions in which it is to be employed. 

Hardness. 

Considerable information in regard to the suitableness of a 
water for boiler use may be obtained by testing the " hardness," or, 
in other words, the soap-destroying power of a water. 

Those mineral substances occurring in water which have a 
tendency to corrode a boiler, or to produce scale, have also the 
property, in general, of decomposing a solution of soap with the 
formation of an insoluble metallic soap, so that the measure of 
the soap-destroying power will be roughly a measure of the 
" scale-formers " in the water. 

Free acids also have the power of decomposing soap solutions 
by combining with the alkali of the soap and setting free the 
fatty acids. All the results obtained in water analysis are from 
custom generally expressed in grains per gallon. 

For the determination of the hardness of water, a standard 



404 • THE CHEMISTRY OF PAPER-MAKING. 

solution of soap is made by dissolving 10 grammes of good, white 
Castile soap in dilute alcohol (about 40 per cent.) to make 1000 c.c. 
One cubic centimetre of this solution should be able to precipitate 
a soluble calcium salt equivalent to 0.001 gramme of carbonate of 
lime. On account of the varying amounts of moisture in Castile 
soap, however, it is only as we may say by accident that we are 
able to obtain from 10 grammes of soap, a solution of exactly this 
strength. It is always necessary then to verify the soap solution 
by an actual experiment upon water containing a known amount 
of a calcium salt. For this purpose, we may weigh exactly 1 
gramme of powdered marble, or Iceland spar, and dissolve it in 
a covered beaker, in a slight excess of dilute hydrochloric acid. 
The excess of acid is then neutralized by ammonia in very slight 
excess and the solution made to 1000 c.c. Each cubic centimetre 
of this solution will then contain lime equivalent to 0.001 gramme. 
In order to test the standard soap solution, 10 c.c. of the dilute 
lime solution just mentioned is measured accurately and placed in 
a wide bottle or flask holding about 200 c.c. 90 c.c. of distilled 
water are then added and the flask shaken. The standard soap 
solution is then run in from a burette, a little at a time, the 
stopper being inserted and the flask vigorously shaken after each 
addition until a distinct lather is formed which covers the sur- 
face of the liquid in the flask, and which will remain as a thin, 
unbroken pellicle for five minutes. 

The lather should not be thick and frothy, but thin, and when it 
breaks, the liquid will show in patches beneath. When this point 
is reached, the number of cubic centimetres of soap solution used 
is read off, and the milligrammes of carbonate of lime equivalent 
to each 'cubic centimetre found by dividing 10, the milligrammes 
in the 10 c.c. of lime solution used, by the number of cubic centi- 
metres of soap solution employed. 

The standard soap solution will preserve its strength indefinitely 
if kept in a tightly stoppered bottle. 

The total hardness of a sample of water is tested by measuring 
100 c.c. of the sample, and treating it with soap solution as 
described above. 

If 100 c.c. of the sample are found to consume more than 16 c.c. 
of the soap solution, a less quantity of the water must be taken 
and diluted to 100 c.c. with distilled water for the test, as the 
presence of any considerable amounts of lime or magnesia soaps 



WATER ANALYSIS. 405 



interferes with lathering, and consequently with the accuracy of 
the test. The number of cubic centimetres of soap solution con- 
sumed, multiplied by the value per cubic centimetre, as above 
determined, gives the equivalent carbonate of lime in milligrammes 
in the amount of water taken for the test. This figure may be 
converted into equivalent grains per gallon by the proportion — 

Cubic centimetres employed for test : cubic centimetres in 1 gallon (3785) 
= grammes found x 15.4 : grains per gallon. 

It will be noted that we have used the term " equivalent " car- 
bonate of lime above, and it must be borne in mind that this figure 
expresses not only the actual carbonate of lime present, but includes 
also the iron and alumina, and sulphate and chloride of calcium 
and magnesium present, expressed in terms of equivalent carbonate 
of lime. 

Carbonate of lime, CaC0 3 , is almost completely insoluble in pure 
water, but in those waters which hold carbonic acid in solution, as 
is the case with a majority of natural waters, especially those of 
springs and deep wells, it is soluble to no inconsiderable extent. 
The carbonate of lime thus held in solution by carbonic acid gives 
to a water what is called 

Temporary Hardness. 

The determination of the temporary hardness of a water is of 
even more importance in determining its fitness for boiler use than 
is the determination of the total hardness, especially if the water 
contains sulphate of lime, since on boiling the carbonic acid is 
driven off and the carbonate of lime previously held in solution 
by it falls in the shape of a fine powder. Now, if sulphate of 
lime is also present, it is gradually deposited as the water evapo- 
rates, being soluble only one part in one hundred parts at 60° F. 
and less soluble at higher temperatures, and serves to cement the 
particles of carbonate firmly together into a hard crust or scale. 

The temporary hardness of a sample of water is determined by 
boiling 100 c.c. of the water in a flask for, at least, a half-hour. 
It is then cooled and again made to 100 c.c. with distilled water 
and titrated with the standard soap as described above. The 
number of cubic centimetres of standard soap used calculated to 
equivalent carbonate of lime, and this again to equivalent grains 



406 THE CHEMISTRY OF PAPER-MAKING. 

per gallon, gives the permanent hardness of the sample. The 
difference between the permanent and the total hardness is the 
temporary hardness. 

Clark's process for softening water consists in the removal of 
the temporary hardness by the addition of a small quantity of 
caustic lime, which combines with the carbonic acid present to 
remove it from solution as carbonate of lime. The removal 
of the carbonic acid also allows the carbonate of lime which it had 
previously held in solution to be precipitated, and thus destroys 
the temporary hardness. 

Clark's process is of no value as regards permanent hardness. 

A water which shows by the soap test a permanent hardness of 
only two or three grains of CaC0 3 per gallon with no temporary 
hardness, and whose reaction is neutral or faintly alkaline to litmus, 
may with very little question be considered fit for use in a steam 
boiler. 

On the other hand, the hardness of a water as measured by the 
soap test does not necessarily condemn its use in a boiler. It indi- 
cates, however, the desirability of a more extended chemical exam- 
ination before deciding on its fitness for that purpose. Sulphate 
of magnesium, for instance, would decompose soap, and, if this 
substance alone were present, a water might show almost any 
degree of hardness, but such a water would never, under ordinary 
circumstances, form scale in a boiler. 

If the soap test has indicated that a further examination of the 
water "is advisable, we next proceed to determine the 

Total Solids. 

For this purpose, having cleaned, ignited, and weighed a plati- 
num dish, we place in it 100 c.c. of the water and evaporate it to . 
dryness over the water-bath. If only a very little residue appears 
to be left, it is well to evaporate 150 c.c. more, making ^ litre in 
all, to dryness in the same dish. The residue is then heated to 
130° C. in an air-bath, and after cooling is weighed. This gives, 
deducting the weight of the dish, the total solid matter in the 
amount of water evaporated, and this is to be calculated into 
grains per gallon by the proportion — 

cubic centimetres evaporated : cubic centimetres in 1 gallon = grammes 
weighed x 15.4 : grains per gallon. 



WATER ANALYSIS. 407 

The dish is then ignited at a low red heat until the residue is 
white. After cooling, the residue is moistened with a solution of 
ammonium carbonate, or, better still, with a little carbonic acid 
water (a syphon of " soda water " answers the purpose well), to 
replace any carbonic acid which may have been driven off by the 
ignition, and again dried over the water-bath, heated to 130° C, 
cooled, and weighed. The weight of the last residue gives the 
total mineral matter present, and this deducted from the first 
residue, or the total solids, gives the organic and volatile matter 
by difference. 

The amount of the inorganic or mineral solids obtained from 
the portion evaporated as above will serve to determine how much 
of the sample must be concentrated for the examination of the 
mineral constituents. Enough should be taken to give at least 
1 gramme of total mineral matter. Two grammes would be pref- 
erable, if the evaporation of the requisite amount of the sample 
is not too tedious. The sample to be evaporated for the latter 
purpose should be acidified with a few drops of hydrochloric acid, 
and evaporated in a platinum dish over the water-bath, adding a 
portion of the sample from time to time as it evaporates, until it 
has all been transferred to the dish. It is finally evaporated to 
dryness, and, after breaking down any lumps with a glass rod, is 
heated over the water-bath until the residue no longer smells of 
hydrochloric acid, in order to render insoluble any silica that may 
be present. After cooling, it is moistened with hydrochloric acid, 
and taken up with water, and the solution filtered from insoluble 
matter, which latter will consist of the silica and very likely a 
little organic matter. This is well washed over the filter with hot 
water and, after drying, ignited and weighed. The organic matter 
will, of course, be destroyed by the ignition leaving the silica 
pure white. 

To the combined filtrate and washings from the silica ammonia 
is added in slight excess, and the whole heated very nearly to 
boiling for some time, until the odor of ammonia can no longer be 
detected. This serves to separate any alumina and sesquioxide 
of iron, and these should be filtered out and well washed with 
hot water, dried, ignited, and weighed. The filtrate and wash- 
ings should next be concentrated to 100 c.c. or less, and 
an excess of ammonium oxalate solution added to separate the 
lime. Both the solutions should be hot before being mixed; 



408 THE CHEMISTRY OF PAPER-MAKING. 

otherwise the oxalate of lime is apt to precipitate in a very 
finely divided condition and to give trouble by passing through 
the filter. The solution, after the oxalate is added, should be 
kept hot for a little time, until the precipitate has settled nearly 
clear. It is then filtered, and the precipitate washed with hot 
water. The oxalate of lime precipitate is dried, and ignited 
'strongly for some time, and weighed. After weighing, it should 
again be ignited and weighed, and this repeated until a constant 
weight is obtained. The final weight is the weight of the lime, 
CaO, present. The filtrate and washings from the oxalate of lime 
are allowed to become cold, and then a large excess of ammonia is 
added and some solution of pure phosphate of ammonia to pre- 
cipitate the magnesia. After stirring, this is allowed to stand for 
several hours for the precipitation of the magnesia to become 
complete. The precipitate is then filtered off, and washed with a 
mixture of 8| parts by volume of water and 1^ parts of strong 
ammonia. The precipitate is dried and ignited strongly, and 
weighed as magnesium pyrophosphate, Mg 2 P 2 7 , which multi- 
plied by 0.3604 gives the equivalent magnesia, MgO. 

This completes the separation of all the bases ordinarily present 
in water except the alkalis. For the determination of these, the 
filtrate from the magnesium phosphate precipitate is to be evapo- 
rated in the platinum dish to dryness and ignited gently until no 
more fumes appear, taking care only to barely fuse the residue. 
The residue is dissolved in water and filtered from any undissolved 
matter, and the filter well washed. The filtrate and washings are 
returned to the clean platinum dish, a few drops of ammonium 
chloride solution added, and again evaporated to dryness and 
ignited. It is cooled in the desiccator and weighed, and the weight 
of the dish deducted, leaving the weight of the mixed chlorides of 
sodium and potassium, NaCl + KCl. The chlorides are next 
dissolved in the dish with a little water and some solution of 
platinic chloride added, and the whole evaporated almost to dryness 
over the water-bath. It is then removed from the bath and some 
80 per cent, alcohol poured over the mass in the dish before it has 
had time to cool. It is covered and allowed to rest for some time 
and then filtered through a small filter, which has been tared by 
means of a similar filter placed on the opposite scalerpan, and 
trimmed until the two exactly balance. 

The precipitate, which should consist of platinochloride of 



WATER ANALYSIS. 409 



potassium, K 2 Pt.Cl 6 , should be bright and crystalline. It should 
be washed on the filter with 80 per cent, alcohol until the washings 
come off entirely colorless. The precipitate and the tared filter 
should be dried in the water-oven and weighed, the tared filter being 
placed on the scale-pan opposite the one containing the filter 
carrying the precipitate. The weight of the precipitate multiplied 
by 0.1932 equals equivalent potash, K 2 0, or multiplied by 0.3057 
equals equivalent potassium chloride, KC1. 

The weight of potassium chloride thus found, deducted from 
the weight of the mixed chlorides, as determined above, leaves the 
weight of the sodium chloride, NaCl, and this multiplied by 0.5306 
gives the equivalent soda, Na 2 C This completes the determina- 
tion of the bases. 

A separate portion of 250 or 500 c.c. of the water should be 
measured and acidified with hydrochloric acid and evaporated to a 
small volume, say about 100 c.c. for the determination of sulphuric 
acid, S0 3 . The concentrated water should be filtered if necessary 
and an excess of barium chloride solution added, and the SO g 
weighed as barium sulphate (compare determination of S0 3 in 
Soda Ash). 

Still another portion of 250 or 500 c.c. is to be taken for the 
determination of chlorine, CI. This portion should be evaporated 
tvithout the addition of acid to about 50 c.c, and after cooling, 
titrated with standard silver nitrate solution by the aid of chromate 
of potash (compare estimation of chlorine in Sodium Chloride). 

This completes the examination of the solid residue, it being 
rarely necessary to make a determination of carbonic acid directly. 
As yet, however, we have very little knowledge of the character 
of the mineral matter present in the water we have examined, and 
to obtain such knowledge, it is necessary to translate the language 
of our analytical data into that of the several compounds, as they 
exist in the original sample. Experience, coupled with direct 
experiment, has shown the manner of 

Grouping the Constituents 

to be as follows : The chlorine is combined with soda as sodium 
chloride, NaCl. Any excess of chlorine over that required by the 
soda found is combined with potash, magnesia, and lime in turn. 
Any excess of soda over that required to form NaCl with the 



410 THE CHEMISTRY OF PAPER-MAKING. 

chlorine is calculated to sulphate of soda, Na 2 S0 4 , and the re- 
mainder of the sulphuric acid is to be combined with potash, 
magnesia, and lime in the order named. Any excess of bases yet 
remaining uncombined is to be calculated to neutral carbonates. 

The sum of all these compounds, together with the iron oxide, 
alumina, and silica formed, expressed in grains per gallon should 
be equal to the grains per gallon calculated from the determina- 
tion of the total inorganic solids to the fraction of a grain, other- 
wise the work must be repeated. 

As before remarked, carbonate of lime is very nearly insoluble 
in water, and yet in the water-residue and in boiler scale we 
often find it present in considerable amount ; the explanation of 
this seeming paradox being that the original water was a dilute 
solution of carbonic acid, and that in this solution, carbonate of 
lime is quite appreciably soluble. When, however, the water is 
heated, the free carbonic acid is driven out of the solution, and 
the water being no longer able to hold the carbonate in solution, 
it falls as a precipitate, and is found in the residue or in the 
scale, which is really the same thing. A water which contains 
even two or three grains of sulphate of lime per gallon is unfit 
for use in a boiler unless precautions are taken to guard against 
the formation of scale, and especially if it also shows temporary 
hardness under the soap test. Carbonate of lime alone (which 
is indicated by temporary hardness) makes mud rather than 
scale ; but if sulphate of lime is also present, the latter seems to 
act as a cementing material to make the carbonate into stone on 
the boiler sheets, etc. The addition of soda-ash in the proper 
proportion to water showing temporary hardness and sulphate of 
lime will overcome the scaling tendency almost entirely, but will 
cause a large amount of mud, to get rid of which, the boilers must 
be blown out frequently. 

Waters containing silica are especially troublesome, giving a 
hard, closely adherent scale, sometimes approaching feldspar in 
composition. Soda-ash may also be employed with advantage with 
waters of this class. In every case, however, soda-ash should be 
looked upon rather as a preventive than a cure, since it will only 
seldom serve to loosen up a scale already formed. 

Many so-called scale preventers are in the market, and, like 
other patent medicines, some of them are probably of value. 
Petroleum oil, either crude or refined, is among the best of scale 



WATER ANALYSIS. 411 



preventers, and is equally useful with almost every character of 
water which is likely to form scale. Its probable action is one of 
lubrication, preventing by its presence the cementation of the 
solid particles, and keeping the deposit in the form of mud, in 
which state it is easily gotten rid of. Organic impurities, unless 
present in very excessive amount, are of no very serious impor- 
tance as regards the use of water in steam boilers, as they seldom 
form heavy deposits. 

For Manufacturing Purposes. 

For other purposes, a knowledge of the amount and character 
of the impurities in water is of even greater importance than for 
boiler use. Here, too, the soap test is of much value, since those 
substances which will precipitate soap, or which make a water 
"hard," will also precipitate rosin size, and the precipitate formed 
will have quite different properties from that formed by a salt of 
alumina or an alum. A given amount of size, for example, will 
not size a paper nearly so hard when a hard water is employed as 
it will with a soft water. Especially will this be the case when 
the size is added first and the alum later. When this order is 
followed, the size may even be entirely precipitated by the impur- 
ities of the water before the alum is added, and the alum have no 
effect whatever. In a case of this kind, a little soda-ash, added 
before the size and alum, will help the matter very much. 

For use in paper-making, the absence of organic impurities, and 
especially of such as impart color to the water, is of great impor- 
tance, both in the paper machine and in the bleaching. In using 
a colored water that must be bleached as well as the fibre, it 
often occurs that no small proportion of the bleach required to 
bring a chest or an engine of stock " up to color " is expended 
upon the organic impurities in the water. 

A direct test of the amount of bleaching-powder, or available 
chlorine, a water will destroy may be easily made by adding a 
measured amount of bleaching-powder solution of known strength 
to a given volume of the water, and gently warming for an 
hour, and then determining the available chlorine remaining by 
means of standard arsenic solution. (Compare determination of 
strength of bleaching-powder, under Hypochlorites.) The dif- 
ference between the available chlorine added and that remaining 



412 THE CHEMISTRY OF PAPER-MAKING. 

in the water will be the amount of available chlorine destroyed 
by the amount of water taken for the experiment, or the bleach- 
consuming power of the water. 

Boiler Scales. 

These are ordinarily residues left by the evaporation of the 
water used with the addition of iron oxide corroded from the 
boiler shell, and sometimes a little oil which has found its way 
into the boiler. The presence of the latter may be recognized by 
the odor on heating a sample, and if it is desired the amount may 
be determined by extracting the powdered scale with ether and 
weighing the oil after evaporation of the ether. The analysis of 
the oil-free residue is conducted as in examination of water residue 
(see under Water Analysis). 

BISULPHITE SOLUTIONS. 

The bisulphite solutions are chiefly interesting as being in their 
several forms the basis of all the processes in use for the produc- 
tion of " Sulphite Pulp " from wood. 

The oldest of these processes and the one first introduced into 
this country by Mr. Charles S. Wheelwright of Providence, R.I., 
is known as the " Ekmann Process " and employs as the reduc- 
ing agent a solution of bisulphite of magnesium. 

Without touching on the at present disputed point whether or 
not the bisulphites of the earth bases, as magnesia and lime, really 
exist, we may say that with the Ekmann process, at least, it has 
been proved by experiment that a solution which contains sulphu- 
rous acid, S0 2 , and magnesia, MgO, most nearly in the proportions 
theoretically required to form magnesium bisulphite, MgS 2 O g , 
gives the best as well as the most economical results. 

Estimation of Sulphurous Acid. 
Symbol, S0 2 . — Valency, II. — Molecular weight, 64. 

For the determination of the total sulphurous acid, S0 2 , in a 
solution, we require a standard solution of iodine and some starch 
paste. 

The solution of iodine is prepared by weighing accurately 12.7 
grammes of chemically pure, resublimed iodine on a watch-glass 



BISULPHITE SOLUTIONS. 413 

and transferring the same to a flask. About 18 grammes roughly 
weighed of chemically pure potassium iodide is added to the 
iodine in the flask and about 100 c.c. of water. The whole is then 
allowed to rest with frequent gentle agitation until all the iodine 
is dissolved. Heat must not be used to hasten the solution of the 
iodine, and the flask should be covered or fitted with a glass 
stopper and kept in a cool place during solution. When the 
iodine has all been dissolved, the solution is to be diluted to 
exactly 1000 c.c. and well mixed. This will form a -^-normal 
solution of iodine, each cubic centimetre of which is equivalent to 
0.0032 gramme of sulphurous acid, S0 2 , The strength of the 
solution may be verified by means of the standard arsenic solution 
mentioned under analysis of Hypochlorites, which see. The two 
solutions, if strictly deci-normal, should correspond or neutralize 
each other cubic centimetre for cubic centimetre. 

The actual determination of sulphurous acid is made as follows, 
and the process is the same for all solutions containing sulphurous 
acid, free or combined : — 

The specific gravity of the solutions at 15° C. (60° F.) is first 
ascertained. 

Next, exactly 2 c.c. of the solution is measured and diluted 
with recently boiled water to about 100 c.c. Two or three grammes 
of bicarbonate of soda are added to the solution and a few drops of 
thin starch paste. The standard iodine solution is then run in 
gradually with constant stirring until a point is reached where the 
addition of a single drop of the iodine changes the entire liquid 
from colorless to a blue which does not disappear on stirring. 

The number of cubic centimetres of iodine solution used is then 
read off from the burette. This number of cubic centimetres, 
multiplied by 0.0032, the value in S0 2 of one cubic centimetre, 
gives the grammes of S0 2 contained in the 2 c.c. of the solution 
used for the experiment. 

In order to calculate this figure into per cents., we must take 
into account the specific gravity of the solution tested. Suppose 
we found the specific gravity to be 1.0425, then the 2 c.c. taken for 
the test would weigh (1.0425x2) 2.085 grammes, and the per 
centage of S0 2 would be found by the proportion — 

2.085 : (S0 2 ) found in grammes = 100 : x per cents. 



414 THE CHEMISTRY OF PAPER-MAKING. 

Determination of Sulphuric Acid. 
Reported as S0 3 . — Valency, II. — Molecular weight, 80. 

For this purpose at least 10 c.c. of the bisulphite solution, 
accurately measured, are placed in a covered beaker and an excess 
of strong hydrochloric acid added and the whole boiled for some 
time, the object of boiling with excess of hydrochloric acids being 
to free the solution entirely from sulphurous acid. 

For this purpose more than enough HC1 to combine with all the 
base present should be added and the boiling continued rapidly 
in a loosely covered beaker until no smell of sulphurous acid is 
perceptible. The liquid is then to be diluted to about 100 c.c, and 
the sulphuric acid precipitated with barium chloride solution, as in 
the estimation of sulphuric acid in Soda Ash (which see), being 
weighed as barium sulphate. 

In calculating the grammes of sulphuric acid, S0 3 , formed, 
regard must be had to the specific gravity of the solution tested, as 
explained under determination of sulphurous acid. 

Determination of Bases. 

In the determination of the bases in bisulphite solutions, atten- 
tion must be paid to the presence of both lime and magnesia, even 
in the so-called magnesia liquors, since it is impossible to obtain 
magnesia (as magnesite) entirely free from lime, while, on the 
other hand, the lime used for making bisulphite of lime solutions 
always carries a greater or less proportion of magnesia. 

When, as is sometimes the case, soda-ash is used in connection 
with lime or magnesia in making the liquors, soda is also present, 
which complicates the matter still further. 

When only lime and magnesia are present, it is sufficient, in 
order to determine the amount of each, first to convert the entire 
amount of both the lime and the magnesia into sulphates and 
obtain the weight of the mixed sulphates. 

For this purpose it is only necessary to measure out 10 or 20 
c.c. of the sample with a pipette into a platinum dish (por- 
celain may be used if care is taken in igniting), add sulphuric acid 
in slight excess, and evaporate to dryness over the water-bath. 
The sulphuric acid will combine with all the bases present, while 
the sulphurous acid will be set free and will be volatilized with the 



BISULPHITE SOLUTIONS. 415 

water. It is well to cover the dish with a watch-glass until effer- 
vescence ceases. It may then be removed, rinsed into the dish, 
and the evaporation completed without fear of loss. After drying 
over the water-bath, the mass in the dish is to be heated over the 
naked flame, cautiously at first, to avoid spattering, until no more 
fumes of sulphuric acid appear, and finally to a full red heat. 
It is then cooled in the desiccator and weighed. Deducting the 
weight of the empty dish leaves the weight of the total sulphates 
of the bases present. 

It is absolutely essential that white fumes of S0 3 should appear 
on ignition. If they do not appear, the mass must be again mois- 
tened with dilute sulphuric acid, and dried and ignited a second 
time. The ignited mass should be of a pure white color, or at most, 
only a trifle reddish from a trace of iron which is sometimes present. 
The ignited sulphates should be weighed quickly, since sulphate 
of magnesia after ignition absorbs water rapidly from the air, 
and rapidly increases in weight from that cause when exposed 
to the air. It will be found convenient to calculate the weight 
of the total sulphates of the bases found as above to per cents, on 
the weight of the sample as explained previously. 

In order to separate the lime and magnesia present, the mixed 
sulphates obtained as above, after weighing, are treated with about 
5 c.c. of water and one or two drops of hydrochloric acid, 
breaking down any lumps in the mass with a glass rod. This 
serves to dissolve all the sulphate of magnesia, together with a 
portion of the sulphate of lime. The whole is then rinsed into 
a beaker by the aid of the wash-bottle and the smallest possible 
amount of water ; one or two drops of strong sulphuric acid added, 
and strong alcohol equal to twice the volume of the liquid in the 
beaker poured in. The whole is well stirred and left at rest for 
an hour or longer. It is then to be filtered and the precipitate 
washed two or three times with alcohol of 60 per cent, strength 
to remove acid, and then with alcohol of 40 per cent, strength so 
long as the latter removes anything. This latter point may be 
determined by evaporating a few drops of the filtrate on a piece 
of platinum or on glass, when the presence of any residue will 
indicate that the washing is not completed. When all soluble 
matter is removed by the 40 per cent, alcohol, the precipitate 
remaining on the filter may be taken as pure sulphate of lime, 
and may be dried, ignited, and weighed as such, CaS0 4 . The 



416 THE CHEMISTRY OF PAPER-MAKING. 

weight of CaS0 4 x 0.4118 gives the equivalent lime, CaO, which 
may be calculated to per cents, on the original sample. The weight 
of the sulphate of lime as above deducted from the weight of 
the mixed sulphates found, leaves the sulphate of magnesia, 
MgS0 4 , which x 0.3333 equals magnesia, MgO, which in turn is 
to be calculated to per cents. When soda is present as well as 
lime and magnesia, the best mode of procedure is as follows : — 

First, evaporate 10 c.c, or a larger quantity, to dryness over 
the water-bath, with excess of hydrochloric acid. Take up the 
residue with a few drops of water, and transfer to a beaker, 
rinsing the dish with as little water as practicable to insure 
the removal of the entire substance. Add to the solution in the 
beaker gradually, with constant stirring, a slight excess of strong 
sulphuric acid, and then strong alcohol equal to twice the bulk of 
the liquid. Stir well and allow to stand for an hour or longer. 
This will precipitate all the lime as sulphate, which is to be washed 
on a filter with 60 per cent, alcohol to remove acid, and finally 
with 40 per cent, alcohol to remove all soluble matter, dried, 
ignited, and weighed as sulphate of lime, CaS0 4 , as before. 

The filtrate from the CaS0 4 precipitate is to be evaporated to a 
small volume over the water-bath to expel the alcohol. It is then 
allowed to cool, some ammonium chloride solution added, and a 
large excess of ammonia, and finally an excess of phosphate of 
soda solution, the whole well stirred without touching the sides or 
bottom of the glass with the' stirrer, and allowed to rest for a 
couple of hours. This will precipitate the magnesium as phos- 
phate of magnesium and ammonia. This is to be filtered off and 
washed thoroughly with dilute ammonia (15 c.c. of strong ammonia 
to the 100 c.c), dried, ignited strongly, and weighed as magnesium 
pyrophosphate, Mg 2 P 2 7 , which x 0.3604 gives equivalent mag- 
nesia, MgO. 

For the determination of soda, 10 c.c. or more should be 
placed in a platinum (or porcelain) dish, and baryta water 
added to alkaline reaction. The whole is then to be evaporated 
nearly to dryness, and filtered and washed thoroughly. The filtrate 
which contains all the soda is evaporated, with the addition of a few 
drops of ammonium chloride solution, to dryness over the water- 
bath, and the residue gently ignited, not to fusion, so long as fumes 
of ammonium chloride appear. The residue is dissolved in a very 
little water, and a few drops (excess) of ammonium oxalate added 



ROSIN SIZE. 417 



to precipitate the excess of baryta present added. The solution 
is to be again filtered, and the filtrate evaporated with ammonium 
chloride, and ignited, and the process repeated so long as the 
solution of the ignited substance continues to give any precipitate 
with ammonium oxalate solution. The final residue will consist 
of pure chloride of sodium, which is to be weighed after ignition 
to incipient fusion in the dish, and the weight of the dish deducted. 

The chloride of sodium, NaCl, formed x 0.5306 gives the equiv- 
alent soda, Na 2 0, which is to be calculated to per cents, on the 
original sample, as previously explained. In calculating the com- 
position of a bisulphite liquor from the results of analysis, the 
sulphuric acid formed is always combined with lime. When less 
than enough lime to saturate the sulphuric acid is present, the 
lime present is first saturated, and the balance of the S0 3 calcu- 
lated to sulphate of magnesia, MgS0 4 . 

Excess of lime over that required to combine with sulphuric 
acid present is calculated to calcium bisulphite, CaS 2 5 , since 
monosulphite of calcium, CaS0 3 , is almost entirely insoluble. 
The sulphurous acid, S0 2 , still remaining goes first to form mono- 
sulphite of magnesia, MgSO g , and any excess over the amount 
required for this to form magnesium bisulphite, MgS 2 5 . Any 
excess of S0 2 over the amount necessary to form bisulphite with 
all the lime and magnesia present is counted as free S0 2 unless 
soda is present. In the latter case it goes first to form sulphite of 
soda, Na 2 S0 3 , and second to form bisulphite of soda, NaHS0 3 . 
Any excess over the amount necessary to form bisulphite with the 
total amount of all the bases present is counted as free S0 2 . As 
we have said, the best and most economical liquor is that in which 
the bases and sulphurous acid are present in the exact proportions 
necessary to form the respective bisulphites, and these proportions 
can only vary within narrow limits without causing serious losses 
both in the manufacture of the solution and in the quality of the 
pulp produced, as well as serious difficulties both with the liquor 
apparatus and with the digesters employed. 

ROSIN SIZE. 

Common rosin or colophony consists for the most part of a mix- 
ture of pinic and sylvic acids which, when boiled with soda-ash, 
gradually combine with the soda to form pinate and sylvate of the 



418 THE CHEMISTRY OF PAPER-MAKING. 

alkali, or, as we commonly term the whole compound, resinate of 
soda or rosin soap. 

This rosin soap in a semi-solid state forms the common rosin 
size of the paper mill. As ordinarily met with in the mills, it 
contains from 40 per cent, to 60 per cent, of moisture. The 
amount in a given sample may be determined by drying a sample 
at 100° C. and noting the loss of weight. Rosin soap being hard 
to dry in a mass, a convenient mode of procedure is as follows : — 

The sample (about 5 grammes) in which the moisture is to be 
determined is weighed in a porcelain dish. It is then dissolved in 
the smallest possible quantity of hot alcohol and about 50 grammes 
of sand previously dried and accurately weighed added. The 
alcohol may then be evaporated over the water-bath, and the 
residue dried in the water-oven and weighed. 

Free Rosin. 

If it is desired to estimate the free rosin in a rosin size, the 
sample, about 5 to 10 grammes of the thick size, should be first 
dissolved in strong, hot alcohol and filtered. This will give in 
the solution all the rosin free and combined with soda, while any 
excess of soda-ash which may be present, as well as other impu- 
rities, such as sulphate of soda, sand, etc., will remain insoluble in 
the alcohol, and may be dried and weighed after thorough wash- 
ing with alcohol. 

The solution should be freed from alcohol by evaporation over 
the water-bath and the residue taken up with 50 to 100 c.c. of 
water. The solution is next transferred to a separator, which con- 
sists of a pear-shaped or cylindrical glass vessel provided with a 
glass cock below and a glass stopper in the top. About 50 c.c. 
of strong ether is added, and the whole well (though not too vigor- 
ously) agitated, and the two liquids allowed to separate into two lay- 
ers ; the upper of the two layers of liquid being the ether which 
has dissolved out the free rosin, and the lower aqueous solution 
containing all the combined rosin. The aqueous solution is to be 
drawn off as closely as possible, and the ether solution washed 
once or twice with a small quantity of cold water. It is then 
transferred to a weighed vessel and the ether allowed to evapo- 
rate, and the residue heated to 100° C. for a few moments to drive 
off traces of moisture, cooled, and weighed. 



BOSIN SIZE. 419 



A white size may carry 25 to 30 per cent., or even more, of free 
rosin, on the dry basis, while a good brown size should carry 
scarcely any free rosin. 

The amount of combined rosin may be readily determined by 
simply returning the water solution, from which the free rosin has 
been removed by shaking with ether as above, to the separator, 
adding an excess of dilute sulphuric acid, which serves to free the 
rosin from combination, and again washing out with ether, evapo- 
rating, and weighing, as in estimation of free rosin. 



420 



THE CHEMISTRY OF PAPER-MAKING. 



CHAPTER IX. 



PAPER-TESTING. 



Comparatively little attention has been paid in this country 
to the chemical and. microscopical examination of papers, although 
in Germany much work in this direction has been done by Herz- 
berg, Martens, Hartig, Weisner, and others who have so far de- 
veloped their methods and brought their results into line with 
practical work that paper-testing is now one of the regular 
departments of the Koniglichen Mechanish-Technischen Versuchs- 
Anstalt at Charlottenberg, and in similar institutions at Berlin 
and elsewhere. As a result of this work, official specifications 
are now prepared under a system of classification, to which papers 
must conform to be regarded as Normal Papers, so-called. Ac- 
cording to their composition normal papers are divided into four 
classes : — 

Class I. — Paper composed entirely of rags, and with 2 per cent, of 

ash as a maximum. 
Class II. — Paper composed of rags, with admixture of sulphite pulp, 

straw, or esparto, but free from ground wood, and with not over 

5 per cent, of ash. 
Class III. — Paper composed of various fibres, but without ground 

wood, and with 15 per cent, of ash as a maximum. 
Class IV. — Paper composed of various fibres, whatever the per cent. 

of ash. 
Each paper must be well sized, and without free acid. 

Upon the basis of physical character there is the following 
classification : — 



Classes. 



a. Mean breaking length in metres 
/>. Mean elasticity (per cent, of stretch) 
c. Resistance to rubbing 



1. 


2. 


3. 


4. 


5. 


6000 


5000 


4000 


3000 


2000 


4.5 


4.0 


3.0 


2.5 


2.0 


6. 


6. 


5. 


4. 


3. 



1000 
1.5 
1. 



PAPER-TESTING. 421 



While these classifications may be useful as affording a means for 
the ready statement of the characteristics of a paper, it is impossible, 
in our opinion, to divide papers rigidly into a few classes in such 
a manner as to have the classification a direct exponent of their 
value ; and there is always danger under any such system that, 
by a strict adherence to it, one may overlook in case of a given 
paper the special qualities which fit it for a given use. It is 
nevertheless true that these German methods have the advantage 
of giving greater definiteness to the statement of the factors upon 
which the value of a paper depends, and leave less to the caprice 
or personal equation of the buyers, and the classification may be 
disregarded without detracting in the least from the value of the 
methods upon which it depends. We shall, therefore, in the 
course of the present chapter consider these methods somewhat 
in detail. 

Right and Wrong Sides of Paper. — Nearly all papers, except 
those which have been coated, have a different texture or surface 
upon their different sides, and the quality of printing done upon 
such papers depends largely upon which side the impression is 
made. In hand-made papers the wire side is regarded as the right 
side, although this is rather an anomaly, since the best impression 
is obtained upon the upper side. In machine-made papers the 
reverse is the case, so far as nomenclature is concerned, and the 
wire side is properly said to be the wrong side. It may usually, 
especially in wove papers, be detected by the small diamond- 
shaped depressions due to the wire, and called the wire mark. 
The roughest side is not invariably the wrong side, as, for instance, 
in case of paper for crayon and chalk drawing, where the right 
side is the roughest one. Upon opening a ream of unfolded or 
" flat " paper, the upper side is the right one, and if the paper is 
folded into quires, it is right side out. According to Parkinson, 
machine-made, azure laid, yellow wove, or blue papers are usually 
darker on the wrong side, while, if hand-made, the right side, so- 
called, is the darker. 

Direction in which Paper came from the Machine. — This 
is sometimes important, especially when cutting strips to deter- 
mine the strength of paper, since the sheet is always stronger in 
the direction in which it came from the machine than along its 
width. In case of paper made upon a cylinder machine, this 
point is very easily determined, since the fibres are so laid in such 



422 



THE CHEMISTRY OF PAPER-MAKING. 




Fig. 



a paper that it tears in a straight line along the length of the 
machine, and in an irregular, jagged one at right angles to the 
line marking this direction. The direction in which a machine- 
made paper was run off, may be found by cutting from the sheet 
a circular piece about 10 cm. in diameter, 
floating this upon water for a few seconds, 
and then raising it carefully and placing 
upon the palm of the hand. The disc will 
begin to curl, until finally the opposite edges 
meet, forming a sort of tube. The direction 
of the axis of this tube or cylinder gives 
the direction in which the paper came from 
the machine. If water-leaf or unsized paper 
is taken for the test, it must first be dipped 
in a weak solution of rosin in absolute alco- 
hol, and dried before placing in the water. 
Another and simpler method for determining this direction is 
to cut one strip about one-half an inch in width and four inches 
long from the paper lengthwise of the sheet, and a similar strip 
across the sheet. The strips should be marked when cut. If 
when held at one end by the thumb and forefinger, as shown in 
Fig. 89, the strips remain closely together, as there shown, the 
lower strip came from the direction in which the paper was run 
off. If the strips fall apart, as in Fig. 90, 
the upper strip is the one which shows this 
direction. 

Water Marks. — An examination of the 
water marks and the size and character of 
the wire marks is sometimes of the first im- 
portance in establishing the age or identity of 
a sample of paper, but the inferences drawn 
from such inspection are not always conclu- 
sive. It is, of course, not a difficult matter 
to imitate a water mark, and we have seen 
samples in which not only the marks, but the 
characteristics of the stock, and even of the dirt observed in 
ancient papers, were closely reproduced. Many designs having 
the appearance of a water mark, and which are in some cases 
of high artistic merit, are now produced in paper by subjecting 
the sheet to heavy pressure under a die. Legitimate water 




Fig. 90. 



PAPER-TESTING. 423 



marks may, in this way, be closely imitated, so that occasions 
may arise when it becomes important to determine the manner 
in which the marks were made. The true water mark made 
by the dandy-roll, or by wires on the bottom of the mold, is 
thinner than the rest of the sheet, for the reason that there is 
actually less material where the lines occur than would be the 
case if they were absent. The spurious mark is thinner, merely 
because the material has been compressed; the lines contain as 
much fibre as any similar portion of the paper. Wetting the 
paper with strong caustic soda solution, therefore, renders the true 
mark more conspicuous, but obliterates the spurious one. 

Finish and Evenness of Sheet. — There is no method of mak- 
ing a quantitative estimate of either of these factors which have 
so important a bearing in determining the market value of paper, 
and one can only gain the needful accuracy of judgment by the 
study and comparison of many different sheets with reference to 
their intended use. In general, smoothness and evenness of tex- 
ture are more desirable in book papers than an extremely high gloss, 
which is apt to be trying to the eyes. 

Papers in which the fibre is long and has been little beaten are 
usually rather uneven or " wild," as will be noticed on holding 
them to the light. In such papers the finish is higher on the 
thicker portions, and on looking across them at the light appears 
blotchy and uneven. This is a frequent characteristic of all-sul- 
phite paper, and if unbleached sulphite has been used, the effect is 
heightened by the natural gloss of the hard fibre. A " hairy " look, 
due to the projection of the ends of fibres from the surface, is 
objectionable, as is also any tendency for the filler to leave the 
paper as " dust." This is noticed upon drawing the paper over a 
black coat-sleeve, and causes trouble in printing, by clogging and 
filling the type, and especially the fine lines of process cuts. 

Dirt. — The common way of detecting dirt in paper is by hold- 
ing the sheet to the light ; but this method is not altogether fair 
to the paper-maker, since in use it is generally only the surface dirt 
which shows or is objectionable. This surface dirt may be brought 
into prominence by drawing a small circle around the larger specks. 
In this way the comparative cleanness of two or more sheets for 
the purposes of practical work may be determined at a glance. 
The character of the dirt is of more importance to the paper-maker 
than to the consumer. Shive and lumps of fibre are usually 



424 THE CHEMISTRY OF PAPER-MAKING. 

detected at once by their comparatively large size and general 
appearance. If due to uncooked wood, their color is intensified 
by a drop of aniline sulphate solution. Slime marks and size spots 
are more or less transparent, and if large, break the continuity of 
the sheet. Fine particles of iron from the engine rolls are far 
more numerous in paper than is commonly supposed. They may 
be distinguished from other dirt by moistening the paper with ver} 7 
weak hydrochloric acid, then allowing it to dry and dipping in a 
weak solution of ferrocyanide of potash. Each bit of iron then 
stands out surrounded by a blue zone. Spots due to filler or to 
calcium sulphite derived from sulphite pulp are usually nearly 
white, and break up under the point of a pin into many smaller 
particles. Mica in the filler is perhaps not properly dirt, but is 
equally noticeable from its shiny appearance, which causes it to 
stand out upon the surface. 

Other dirt may consist of bits of bark or leaves or other vege- 
table matter derived from the water or the pulp. Particles of coal, 
tiny fragments of copper, and many other things find their way 
into the paper, either from the air or more commonly from the 
stock or chemicals. Their exact nature can usually be determined 
by simple chemical tests or by a microscopical examination, and 
not infrequently their source may be thus pointed out. 

Mechanical Testing- : Thickness. — This is determined by means 
of an ordinary screw micrometer gauge with divisions giving thou- 
sandths of an inch, while the spaces between divisions may be read 
to one or two ten-thousandths. The ends of the micrometer which 
touch the paper should have rather wide disks or flanges, and care 
must be taken not to compress the paper in bringing them down 
upon it. It is often important to compare papers with reference to 
their so-called " thickness for weight." A direct numerical com- 
parison may be made by first figuring the weights of the papers into 
sheets or reams of equal size and dividing the weight of each by 
the thickness in ten-thousandths of an inch. The weights of equal 
thicknesses of the papers are then directly proportional to the 
quotients obtained. Where other things are equal, laid papers are 
always thicker for weight than wove. 

Mechanical Testing-: Strength and Stretch. — The strength of a 
paper is the quality to which attention is usually first directed if its 
general appearance is in any way satisfactory. It is usually deter- 
mined in this country either very roughly by tearing or more accu- 



PAPEB TESTING. 



425 



rately by testing-machines which give only relative results useful 
for direct comparisons. The stretch which is of especial importance 
in papers used for lithographic work or for other purposes for which 
an accurate register is necessary is not determined at all. Several 
paper-testing machines which give both the strength and stretch of 
paper in absolute terms which permit of strict comparison without 
reference to the width or thickness of the samples are now in com- 
mon use in Europe, and will be noted in some detail. The one 
which has found most general introduction in the institutions de- 
voted to paper-testing is the Wendler apparatus shown in Fig. 91. 
To obtain accurate information about the quality of paper with 
respect to strength and stretch, a strip of definite length and width 
is cut from the sheet, and is then strained either by weights or a 
spring of known strength, until it breaks. The measure of the 
strain gives the fracture weight, and the stretch of the strip up 
to the point of fracture is called the fracture stretch. For com- 
plete data, the paper should be thus tested both with the length 
of the machine and across it, since both the strength and elasticity 
of the paper vary with the direction in which the strip is cut. 
The power needed to tear the strip is no criterion of the strength 
of the stock from which the paper is made, as it gives merely the 
strength with which the fibres have felted, and varies also with 
thickness of the sheet. The strength of paper is expressed in 
Germany in terms of fracture length, the fracture length being the 
length of a strip of any width or thickness, which, if suspended by 
its upper end, would have just weight enough to cause the strip to 
break. The following example will show the method of calculat- 
ing the fracture length. Ten strips were cut from the sheet, five 
being with the length of the machine and five across it: — 



WITH THE LENGTH. 


ACROSS THE MACHINE. 




Fracture Strength. 


Fracture Stretch. 




Fracture Strength. 


Fracture Stretch. 


1. 

2. 
3. 
4. 

5. 


17.56 lbs. 
17.44 " 
17.36 " 
17.40 " 
17.60 " 


1.9 per cent. 

1.8 " 

1.8 

1.8 

1.9 

9.2 per cent. 
1.84 " 


1. 

2. 
3. 
4. 

5. 


10.80 lbs. 
10.88 " 
10.60 " 
10.76 " 

10.80 " 


3.6 per cent. 

3.6 

3.4 

3.5 " 

3.5 


87.36 lbs. 
Avg 17.47 " 


53.84 lbs. 
Avg... 10.768 " 


17.6 per cent. 
3.52 " 



1 



426 THE CHEMISTRY OF PAPER-MAKING. 

These tests were made on the Wendler apparatus, and their 
close agreement will be noticed. The average weight of the strips 
was 0.0151 ounces, and in order to figure the fracture lengths, 
one has to determine the length of the strips of the same width 
which will weigh 17.47 lbs. and 10.768 lbs. respectively. Calling 
the unknown length in the first case x, the length of the strip 
taken being 9 inches, we have the proportion : — 

f ft. : 0.0151 oz. = x : 279.52 oz. 
_ !x 279.52 



0.0151 



= 13884 ft. 



Across the machine we have 10.768 lbs., or 172.280 ounces 
fracture strength ; therefore — 

| ft. : 0.0151 oz. = x : 172.288. 

# x 172.288 _ 
X ~ oioisl - 8o57±fc - 

Our data may, therefore, be summed up as follows : — 

With the length . . . 13884 ft. fract. length. 1.84 per cent, stretch. 

Across the machine . 8557 ft. fract. length. 3.52 per cent, strefcch. 

22441 ft. 5T36~per cent. 

Average 11220 ft. 2.68 " 

Upon these figures the paper is classified in the official 
schedules. The calculation is greatly simplified by tables con- 
taining what are known in Germany as fineness numbers ; that is, 
the quotients obtained by dividing the length of the strip by its 
weight. From these tables the number by which we should 
multiply the fracture weight in order to get the fracture length, 
can be at once obtained. Such well-known authorities as A. 
Martens, superintendent of the Berlin Royal Testing Institution, 
Professor Hartig, Professor Weisner, and W. Herzberg, have 
already, as has been stated, done much toward the classification of 
German papers, and the determination by this method of the 
influence of air, light, water, acids, sizing, and pressure upon the 
quality of paper. 

The Wendler apparatus consists essentially of four main parts : — ■ 

1. The actuating mechanism. 

2. The arrangement for holding the strip. 

3. The spring. 

4. The mechanism for measuring the strength and stretch. 



PAPER-TESTING. 



427 



The first consists of a hand wheel, U, or a worm, F. The top 
of the wheel turns in the bearing block, which is cast in one piece 
with the bed. The screw H is tight with the sled K, and is led 
through the nut 6r, which consists of a shell containing a clutch 
which may be thrown in or out by turning the nut about 90°. 

The arrangement for holding the strip consists of two clamps, d 
and /, the first being connected with the spring and the other 
with the sled. The strip is put between the jaws of the clamps, 
which are then pressed together by screws. 

Two springs may be used, one of 20 lbs. strength, and the 
other of 40 lbs., the latter for heavy papers. The spring is 




Fig. 91. — Wendler Paper-testing Apparatus. 

supported at one end by the bed, and at the other end by the 
movable carriage. The rack is connected with the carriage and 
passes through the shell to the rear of the spring, where there 
are pawls which catch in the teeth of the rack and prevent the 
spring from flying back when the paper breaks. 

The strain is measured as follows : The carriage pushes the 
indicator before itself by means of an angle rod. The indicator 
has a zero mark, under which is read on the scale the fracture 
strength after the strip breaks. The stretch is shown in per cents, 
of length by another indicator attached to the sled K. The scale 
above, which this indicator moves, goes forward at the same rate 



428 THE CHEMISTRY OF PAPER-MAKING. 

as the carriage, while, if the paper stretches, the indicator moves 
forward enough faster to take up the stretch, and from its position 
at the end of the test the stretch is read directly. 

To test a paper with this apparatus, the strength scale is 
adjusted by raising the pawls s, bringing the indicator up against 
the angle rod, and the zero marks on scale and indicator together. 
Spring R is held in position by the screw I, which is tightened for 
the purpose. A strip of the paper to be tested is placed between 
the clamps / and d, the clutch Q- is thrown in, and the screw I 
loosened to free the spring, then by the hand, or better, by a little 
water or electric motor, the wheel E is slowly turned until the 
paper breaks. After tearing the strip the breaking strain and 
stretch are read from the scales, and the spring is made to resume 
its normal position by raising the pawls s and slowly letting the 
carriage back. 

The Schopper Testing-Machine. — In using this machine, the 
samples required for testing have first to be prepared. This is 
done as follows : A piece of the sheet is taken and cut to a 
length of 12 inches, and then cut off in strips by the cutting blade, 
fixed upon the scale. The sheet of paper, when the correct 
length is once obtained, is simply put under the knife and rested 
against an edge, beyond which it cannot go. The knife is then 
lowered, thereby cutting off the strip to the needful size. Some 
little care is naturally required to see that this cutting of the 
paper is properly accomplished with due accuracy as to width. 
This the cutter arranges automatically, if carefully and methodi- 
cally handled. After, say, ten or a dozen strips are cut off the 
sample, they are numbered in lead pencil from one to ten, or 
alphabetically, and the position in the sheet whence they come is 
also noted down on each strip. After having correctly obtained 
two sets of strips, one set across, and the other along the direction 
of the paper as it came from the machine, and each having been 
marked, they are next hung upon an ordinary paper scale, and 
the weight of each slip is taken and multiplied by two, which 
gives the equivalent weight of this sample of paper as a ream. 
It is then advisable to note down this figure upon the slip, and 
also, for safety sake, upon a separate sheet of paper. As soon as 
the weights equivalent to a ream have been duly noted, the 
samples are ready for testing. 

The apparatus consists of a levelling stand, upon which there 



PAPER-TESTING. 429 



is a rod or pillar ; near the top of the pillar there are two levers 
pivoted, the shorter and upper portions are curved or bent to facil- 
itate the attaching of other parts thereto, and the lower or longer 
arms are each provided with an index pointer, so that when the 
material is being tested they each traverse graduated arcs. One 
of these arcs is fixed to the pillar and is graduated to indicate the 
pull exerted at the shorter end of the lever. The other arc is 
attached to the weight-indicating lever, and is graduated to show 




Fig. 92. — Shopper Paper-testing Machine. 

the per cent, of stretching prior to fracture by the breaking 
weight. 

The weight-indicating arc is provided with ratchet teeth, and 
the lever with a series of pawls, so arranged that each tooth of 
the ratchet under the pawls is practically divided into fractional 
parts, thus securing strong teeth and avoiding shock by recoil 
when the paper breaks. 

The bent or shorter arms of the lever have suitably pivoted 
connections. In case of the tension lever, or rod, the other end 



430 THE CHEMISTRY OF PAPER-MAKING. 

of which is connected with a slide, the weight lever has a clamp 
for the purpose of securing one end of the paper to be tested ; the 
clamp for the other end is connected with the slide alluded to 
above ; the slide is actuated with a screw, further connected with 
limit cog wheels and with hand-driving wheel, to communicate 
steady, continuous, slow motion to the slide. 

To make the test, a definite length (according to the graduation 
of the tension arc) of paper is fixed between the clamps, in its 
normal straight condition, the index pointers adjusted to zero 
by means provided, then the wheel turned. The screw brings 
the slide down, stretching the paper until it breaks, then one of 
the series of pawls prevents recoil, and the breaking weight and 
tension can be read off. 

The machine must stand level, and this can easily be arranged 
by ascertaining that the weight hangs true, and that the index 
pointer is exactly over the proper mark upon the curved scale 
board. Having settled this matter, and fixed the weight by 
inserting a small pin which rests in the stand, the wheel is duly 
set at its limit, and the screw controlling the tension rod is 
fastened. The sample slip is then inserted into the lower clamp 
and fastened thereby. This is very simply done, by merely bend- 
ing the clamp back, and this causes the paper slip to become 
firmly held. The same is then arranged with the upper clamp, 
the slip of paper being gently but properly held taut by the two 
clamps. 

All being ready, the pin holding the weight is withdrawn, and 
while the small wheel is set slowly revolving, the screw control- 
ling the tension rod is unfastened. The weight at once begins to 
ascend the curved scale board, passing the numbered graduations 
en route. The back of the weight is provided with a set of four 
separate small pawls, which, as the weight ascends the scale board, 
move with it and drop into ratchet teeth in such a way that when 
the sample breaks the pawls stay the weight by their inability to 
move out of the teeth. The figure at which the weight drops is 
indicated by the pointer and denotes the number of pounds which 
represent the force of the strain. Meanwhile, above this pointer, 
and upon a smaller scale board, another pointer has been moving, 
and this indicates the tension of the sample, or the amount of 
stretch per cent, of which the sample is capable. This indicator 
also stops when the paper breaks, thereby permitting a perfectly 



PAPER-TESTING. 431 



accurate reading to be taken. As soon as this has been done, the 
small ratchet teeth are raised and the weight replaced in its 
primary position : the same is also done with the tension pointer, 
which, however, is without any ratchet teeth to control its move- 
ment. 

The Rubbing Test. — The extent to which a paper will bear 
folding and rubbing without breaking has in many cases a con- 
siderable influence in determining its value. It may be tested in 
this respect by crumpling a half sheet strongly in the hand to 
form a sort of ball, then smoothing the paper and repeating the 
operation several times. Papers which, with reference to their 
power of resisting wear, would be classified as " extremely poor " 
on the following scale, which is that adopted by the Germans, soon 
develop holes under this treatment. As the paper succumbs to, 
or withstands, this treatment, or requires in addition, in order to 
make holes, more or less violent rubbing upon itself between the 
hands, it is given a number which has the significance shown 
below : — 

0. Extremely poor. 

1. Very poor. 

2. Poor. 

3. Medium. 

4. Rather good quality. 

5. Good quality. 

6. Very good quality. 

7. Extremely good quality. 

News and similar papers would be marked 0, while a Japanese 
or very strong pure jute paper would be given the number 7. 

Determination of Size. — The methods employed in the 
laboratory of the Koniglichen Mechanish-Technischen Versuchs- 
Anstalt at Charlottenburg, and which have been adopted with 
slight modification in our own laboratory, are thus described by 
Herzberg and others : — 

The test for animal size with tannic acid depends on the for- 
mation of a precipitate of tannate of gelatine. When tannic acid 
is added to a solution of gelatine which is not too dilute, there 
will be formed a thick gelatinous precipitate. In a very dilute 
solution only a milky cloud will be seen, which will, after a short 
time, separate in flocks ; the cloudy appearance without the 
separation of flocks shows the absence of animal size. In carrying 



432 THE CHEMISTRY OF PAPER-MAKING. 

out the test the paper is first treated, as described above, with 
distilled water, and the liquid concentrated as much as possible 
by evaporation, as then it is easier to see the reaction. When the 
solution is cold, a concentrated solution of tannic acid in water is 
added, and care must be taken to observe whether a precipitation 
and separation of flocks takes place. 

When either very small amounts of material are available, as in 
the case of old manuscripts, or where it is necessary to determine 
the presence of very small quantities of animal size, this method 
cannot be used, and the reagent of Millon is alone available for 
the purpose. This reagent is a very delicate test for albumen, a 
substance always present in animal size, and is prepared as fol- 
lows : To a weighed quantity of metallic quicksilver an equal 
weight of fuming nitric acid is added, and the whole allowed to 
stand in a cold place for a few hours ; after which an equal vol- 
ume of distilled water is added, and the whole left quiet for 
twenty-four hours. Prepared in this way the reagent will keep 
active for about four weeks. 

A small piece of the paper to be tested is placed on a watch- 
glass and moistened with the reagent, and then brought on to a 
wire gauze and heated very gradually. If animal size is present, 
in a few minutes the paper will be colored red; the color will 
vary from rose to scarlet, according to the quantity of size which 
is present. As the red color gradually becomes brown, it is 
necessary to watch the paper during the whole reaction. The 
coloration can also be seen in the cold, but only after the reagent 
has acted for a considerable time on the paper, and the coloration 
will never be so distinct as when the paper is heated. It will be 
found advantageous to moisten a sample of the paper to be tested 
with distilled water, and to treat this in the same way as that 
moistened with the reagent, so as to compare the resulting colors. 
The reagent of Millon shows the presence of aromatic groups 
containing a simple hydroxyl ; this being present in albuminoid 
bodies, it is consequently a test for albumen. As commercial glue 
alwa} r s contains albumen (as does even the finest colorless gela- 
tine), the reagent may be used as a test for animal size. However, 
it must be noted that chemically pure gelatine does not contain 
this group ; for practical purposes, however, this is of no conse- 
quence, but the presence of animal size, as found by Millon's 



PAPER-TESTING. 433 



reagent, can only be considered as final under the following sup- 
positions : — 

1. That the paper does not contain albumen as such. 

2. That there are no free aromatic groups with hydroxyl. 

With regard to 1. Albuminoid bodies are very rarely found in 
paper fibres apart from size, and then only as traces. Further 
microscopical research will show whether the fibres give the 
albumen reaction, as in this case the coloration will be in the 
central canal of the cell, while the glue remains on the out- 
side of the fibre. We need not take into consideration those 
cases in which the albumen has been added to the paper for 
special purposes, as in albumenized paper for photography. As 
regards the second supposition, it may be remarked that, apart 
from vanilline, we do not expect to find the forementioned aro- 
matic groups in paper. If vanilline is present as a compound of 
wood, it can be found by phloroglucin and hydrochloric acid, 
which enables us to determine its origin. If the gelatine used for 
sizing is already decomposed, Millon's reagent will no longer show 
it. In testing old writing material, where fine parchment having 
the greatest similarity to paper is often found, it is also necessary 
to take the fibres into consideration ; such parchment will, of 
course, at once be affected by Millon's reagent, not because it has 
been sized, but because it consists of substances containing 
gelatine. 

As to whether the active sizing material in rosin size is free 
rosin, resinate of alumina, or a mixture of both, opinions are as 
yet divided. While Wiirster considers that the sizing of paper 
is caused by free rosin only, Tedesco and Rudel think that the 
active principle is a compound of rosin and alumina. That under 
all circumstances free rosin is present in rosin-sized paper, cannot 
be doubted, and indeed the test described below for rosin-sized 
paper depends on this. 

Half a sheet of the paper to be tested is torn up into small 
pieces and absolute alcohol poured onto it ; the vessel containing 
it is stood in hot water for about half an hour. When rosin is 
present, it is easily dissolved out by the alcohol, as is also resinate 
of alumina to some extent. If this solution is poured into a suffi- 
cient quantity of cold water, the rosin will be precipitated, as the 
dilute alcohol cannot dissolve it. The distilled water will assume 



434 THE CHEMISTRY OF PAPER-MAKING. 

a milky appearance, the intensity of which will depend on the 
quantity of rosin present. 

In the method described by Schuman, a weighed quantity of 
paper is cut into the smallest pieces possible and warmed for a 
considerable time in a porcelain dish with a 4 to 5 per cent, solu- 
tion of caustic soda to 75° C. ; by the action of the soda solution an 
easily soluble rosin soap is formed. The liquid is then filtered off 
and the paper well washed. To the filtrate a sufficient quan- 
tity of sulphuric acid is added to decompose the rosin soap. Sul- 
phate of soda and free rosin being formed, the latter separates 
as a milky precipitate, which is filtered off through a weighed 
filter, well washed and dried at 100° C. To determine the 
weight of the rosin the weight of the filter should be deducted 
from the total weight found. If the milky .precipitate at first 
runs through the pores of the filter, the filtrate is poured back 
onto the filter till the liquor runs clear through. 

Starch is used in sizing to improve the appearance of paper and 
to give it a good finish. The use of starch alone for the purpose 
of sizing is far older than the use of rosin ; starch sizing is but a 
thing of the past. For example, Weisner has found that all the 
papyrus belonging to the Archduke Rainer Avas prepared for 
writing on by means of starch paste. The first known use of 
animal sizing in paper was in the year 1377. 

A solution of iodine is used for testing starch in paper ; if a 
drop of this solution is applied to a paper containing starch, 
it will cause a blue or violet coloration. The iodine solution must 
be very dilute, or the coloration of the paper will be hidden by 
the brown color of the solution itself. 

The quantitative determination of starch may be carried out 
according to a suggestion of Dr. Wurster, as follows : A strip of 
the paper weighing from 0.5 to 1.5 gramme is boiled for a few 
minutes in absolute alcohol containing a drop or two of hydro- 
chloric acid, when the rosin contained in the paper will go into 
solution. The strip is next washed in absolute alcohol, dried 
at 100° C, and the weight determined. The paper which has 
been thus freed from rosin is next boiled with 50 per cent, alcohol 
containing a few drops of hydrochloric acid, until, when moistened 
with iodine solution, it no longer shows a light blue coloration ; 
it is then washed in alcohol, dried at 100° C, and the weight deter- 
mined. The loss in weight is the amount of starch present. 



PAPER-TESTING. 435 



The methods followed in our own laboratory, for the detection 
and estimation of starch in paper, differ from those given above 
and are as follows : — 

In making a qualitative test for starch we do not apply the 
dilute iodine solution directly to the paper, as the distinctness of 
the reaction is apt to be impaired by the color which the paper 
itself takes on even when starch is absent. Instead we tear the 
paper into small bits and boil these for ten or fifteen minutes in 
water. The solution is then poured off and allowed to become 
cold, when a drop of dilute iodine solution is added. If starch is 
present, there is at once developed a pronounced blue coloration. 

The determination of the amount of starch is effected by con- 
verting the starch into glucose by heating with dilute acid, and 
estimating the glucose by means of the well-known method with 
Fehling's solution. The glucose found multiplied by 0.9 gives 
the equivalent starch. 

In the conversion of starch into glucose careful regard must be 
had to the strength of acid employed, and to the manner of heating, 
since under other circumstances cellulose itself is converted into 
glucose. We have found by experiment that a solution containing 
2 per cent, by weight of sulphuric acid (H 2 S0 4 ) does not attack 
cellulose appreciably when the heating is conducted in the water 
oven, while it converts starch completely under the same conditions. 
The best plan of procedure is to boil 5 grammes of the paper with 
about 500 cc. of water for some time to disintegrate the fibre and 
gelatinize all starch. The weight of the solution, which should be 
at least 500 grammes, is determined, and 2 per cent, of sulphuric 
acid added to it. It is then brought again to boiling and transferred 
to the water oven, where it is kept until a drop of the solution 
mixed with a drop of very dilute iodine solution gives no blue 
color. About three hours' heating is generally sufficient. It is 
then allowed to cool, transferred to a litre flask, and potash or soda 
added in excess. The whole is made to 1000 cc, and a portion 
filtered for the determination of glucose by Fehling's solution. 

The extent to which a paper has been sized is usually determined 
in the mills and among buyers by pressing the tongue against the 
sheet and then holding the paper to the light. With a well-sized 
writing paper scarcely any difference is noticed between the por- 
tion thus moistened and the rest of the paper, but other papers 
appear more or less transparent where they have been wetted 



436 THE CHEMISTRY OF PAPER-MAKING. 

according to the extent to which the sizing has been carried. To 
replace this very crude test, Leonhardi has worked out a method 
which indicates with considerable definiteness the thoroughness 
with which the paper has been sized. 

To carry out Leonhardi's method, a solution of ferric chloride 
of such strength as to contain 1.531 per cent, of iron is required. 
This solution is comparable in its power of penetrating the paper 
to the better grades of writing-inks. An ivory ruling-pen of the 
form used by draughtsmen, and with rounded tips 1 mm. apart, 
is used for drawing with the above solution a number of parallel 
lines upon the paper. The lines are allowed to dry, and then a 
weak solution of tannic acid in ether is poured upon the other 
side of the paper. This ether evaporates almost at once, leaving 
the tannic acid. If the paper has been badly sized, the ferric 
chloride solution will have so penetrated to the under side that 
upon pouring on the tannic acid solution dark lines due to tannate 
of iron appear, while with a very well-sized paper only the yellow 
lines caused by the ferric chloride will be noticed when the paper 
is held to the light. 

An objection has been made to the etherial solution of tannin, 
because it may dissolve rosin size to some extent, and a solution in 
water is therefore sometimes and perhaps better used instead. 
This is applied to the back of the paper by a bit of cloth or ball of 
cotton-wool, and the excess is taken up by blotting-paper. 

It is not really necessary to use the ruling-pen for the ferric 
chloride solution, which may instead be dropped upon the paper 
to be tested from a pipette. To eliminate the error due to the 
thickness of the paper the drop may be allowed to remain as many 
seconds as the paper per square metre weighs in grammes. This 
of course is purely arbitrary, but when adhered to uniformly in all 
tests permits of comparison between different papers. At the end 
of the time the unabsorbed solution is removed by blotting-paper, 
and when the spot has dried, the tannic acid solution is applied to 
the other side. Care should be taken to have the drops from the 
pipette of a size as nearly uniform as possible. 

Capillary Power of Blotting-papers. — This may be determined 
with considerable accuracy, by cutting a strip of the paper and 
marking upon it with a pencil the divisions of a millimetre scale. 
The paper is then suspended over water and lowered until it dips 
into the water sufficiently to bring the zero point on the scale at 



PAPEE-TESTING. 437 



the surface of the water. The height in millimetres to which the 
water is drawn by the capillary action of the paper is then noted 
at short intervals up to ten minutes. This may range from about 
100 mm. in case of the best samples, down to 20 mm. in case of 
especially poor ones. 

Free Acids and Chlorides. — If the bleach is not thoroughly 
washed out of the half-stuff or neutralized by antichlor, it does not 
remain in the paper as hypochlorite for any length of time. The 
chlorides formed by its reduction are, however, believed to be 
objectionable, and to hasten the deterioration of the paper. They 
may be detected by cutting a piece about six inches square into 
small bits, covering these with water in a beaker and boiling. To 
the cold solution slightly acidified with nitric acid a few drops of 
silver nitrate solution are added, when chlorides, if present, deter- 
mine the formation of a white precipitate or opalescence. 

Free acid or an acid alum, if the last is present as such, weaken 
the paper in time through formation of hydrocellulose. It is 
difficult to determine free acid qualitatively in the presence of 
alum with certainty, since the alum itself affects the indicators 
used, but for practical purposes it is generally sufficient to boil up 
the paper as in the test for chlorides, and then to add litmus 
solution or congo-red. 

Determination of Ash. — This is a matter of importance to 
both the maker and the buyer of paper, since it enables the one 
to determine what per cent, of the filler used has been retained in 
the sheet, while it points out to the other the extent to which the 
paper has been weighted. The test is very easily carried out 
although in unskilled hands it is apt to give too high results, owing 
to imperfect combustion. Two grammes of paper are taken, and 
after being folded into as small a compass as possible are placed in 
•a crucible, and the cover put on. A moderate heat is then applied 
until no more smoke or inflammable vapor appears. The crucible 
is then placed on its side upon the triangle, and the cover is 
inclined so as to throw the heat well into the crucible. The whole 
is raised to bright redness, and this temperature is maintained until 
the ash is white, if the paper were not colored, or in any case 
until all carbon is burned off. The crucible and its contents are 
cooled in a desiccator and weighed. From this weight is taken 
the weight of the crucible, and the remainder is of course the 
weight of the ash. This divided by 2 gives the per cent, of ash, 



438 THE CHEMISTRY OF PAPER-MAKING. 

which for most practical purposes may be taken without cor- 
rection as representing the percentage of the mineral filler in the 
sheet. 

In very careful work, allowance may sometimes be made for the 
ash normally derived from the fibres composing the paper ; the 
figures obtained by several chemists are given below : — 

Ash in Commercial Pulps. 
W. Herzberg. 

Per cent. 

Sulphite (1) 0.48 

Sulphite (2) 0.51 

Sulphite, bleached . 0.42 

Soda 1.34 

Soda, bleached 1.40 

Straw 2.30 

Straw, bleached 1.34 

Ground wood (pine) 0.43 

Ground wood (fir) .......... 0.70 

Ground wood (aspen) 0.44 

Ground wood (lime) 0.40 

Linen 0.76 

Linen, bleached 0.94 

Cotton 0.41 

Cotton, bleached 0.76 

Ash in Fibres. 
Dr. Muller. 

Per cent. 

Cotton 0.12 

Fine heckled Flemish flax 0.70 

Italian hemp 0.82 

China grass 2.87 

Rhea 5.63 

Jute 1.32 

Phormium tenax 0.63 

Best Manila hemp 1.02 

Esparto . . 3.50-5.04 

Adansonia 4.72-6.19 

Sulphite fibre (Dr. Frank) 0.46-2.60 

Soda fibre (Dr. Frank) ...... 1.00-2.50 



PAPER-TESTING. 439 



Various other determinations will be found in the chapter on 
Fibres. We have ourselves tested samples of cotton half-stuff in 
which the ash ranged from 0.13 to 0.57 per cent. Our figures for 
ground spruce wood are from 0.25-0.32 per cent., while in case of 
sulphite pulps the ash has varied from 0.22 per cent, to over 9.00 
per cent. 

The difficulty at once met in any attempt to correct the ash by 
means of the figures given above, is that these figures themselves 
are liable to vary so much according to the thoroughness of the 
different treatments to which the fibres have been subjected that 
there is danger of introducing a considerable error in attempting 
to guard against a slight one. 

In order to obtain results which fairly represent the average of 
mineral matter in the paper, several samples should be tested. An 
uneven pull on the suction boxes may easily cause the amount of 
filler to vary by 2 per cent, on the different sides of the machine. 
Owing to settling and other causes, an even greater difference may 
appear in the different stages of a run. 

Determination of the Kind of Filler. — This is necessary if 
one desires to know accurately the amount of weight actually added 
to the paper or the exact percentage of fibre which the paper carries. 

A test showing the ash to contain large amounts of silica and 
alumina is all that is needed to prove the presence of clay. To 
make this test, transfer the ash to a porcelain dish, add sufficient 
hydrochloric acid to moisten thoroughly, and then bring the con- 
tents of the dish to a temperature of 120-130° C. on a sandbath 
until all the acid is driven off. The ash is then boiled up with 
water to which a few drops of hydrochloric acid are added, and 
the whole finally thrown on a filter. A white residue on the filter 
is silica. If ammonia added in very slight excess to the hot fil- 
trate throws down a flocculent, bulky, white precipitate, alumina is 
present. The precipitate may be more or less colored if iron also 
is present. 

To some of the above liquid cleared either by filtering or by 
decantation, add ammonium oxalate solution. If there is a slight 
cloudiness, it is doubtless due to lime derived from the clay, but a 
considerable precipitate indicates that the ash contains sulphate 
of lime, and that the filler used was either pearl hardening, 
fibrous alumine, or gypsum. Either of these fillers, if used with- 
out clay, should give a very white ash entirely soluble in water 



440 THE CHEMISTRY OF PAPER-MAKING. 

acidulated with hydrochloric acid : 300-400 c.c. of water in suc- 
cessive portions should be used in all. Such ash rarely contains 
grit, and often shows a needle-like crystalline structure' when 
examined under a hand glass. 

Agalite also gives a very white ash, but this rubbed between the 
teeth shows grit. It should give a test for silica and magnesia, 
both in large amounts. The test is made by fusing the ash in the 
crucible with about five times its weight of a mixture of potassium 
and sodium carbonates in equal amounts. The fused mass is 
dissolved in water, and after solution is complete, a few drops of 
hydrochloric acid are added. The solution is then run down 
to dryness in a porcelain dish, ignited at 130° C, until the acid 
is driven off, then boiled up with water and filtered. 

A white residue on the paper is silica. The filtrate is tested for 
magnesia, as described under Magnesia. 

The ash from any paper rarely contains a notable quantity of 
alumina derived from alum used in sizing. 

If the examination outlined above shows the ash to consist of 
sulphate of lime, the percentage of ash found should be multiplied 
by 1.26 to find the percentage of the filler actually in the paper. 
This is because the sulphate of lime, as it exists in the paper, is 
combined with two molecules of water of crystallization, which 
add proportionately to the weight of the paper, but are driven off 
upon ignition of the ash. Clays also often have a definite per- 
centage of combined water, which, although present in the paper 
to make weight, is similarly driven off on ignition. This percentage 
varies, however, in different clays, so that no general factor can 
be given for use in all cases. The amount of this combined water 
should be determined in the clay used and the proper factor found. 
The per cent, of ash multiplied by this factor gives the percentage 
of weight actually due to the clay in the paper. This corrected 
percentage subtracted from 100 gives the per cent, of fibre in the 
sheet. To figure retention, divide the pounds of fibre furnished 
by the per cent, of fibre in the paper. The quotient is the pounds 
of paper made from the engine. From this figure subtract the 
pounds of fibre furnished, and the balance is the pounds of filler 
retained. This figure divided by the pounds of filler furnished 
gives the percentage of the filler retained. 

If mineral colors have been used in making the paper, some- 
thing toward their recognition may be deduced from the character 



PAPER-TESTING. 441 



of the ash. Iron is recognized by the brown color of the ash, 
and may be determined by fusing as under Agalite, and treating 
the hot solution with ammonia. Its presence in considerable 
amount may indicate ochre, Venetian red, Indian red, or Prus- 
sian blue, the color of the paper being of course an aid in reach- 
ing a conclusion as to which of these colors is present. Chromium, 
if lead is absent, indicates chrome green. In the presence of 
lead it indicates chrome yellow, or if the paper is red, a basic 
chromate of lead. Lead alone, if the paper is buff, is probably 
derived from orange mineral. Ultramarine colors the ash blue, 
and its amount may be determined in many cases by carefully 
igniting a considerable quantity of the paper until all carbon has 
been burned off, then taking a quantity of ignited clay or sulphate 
of lime equal to the weight of the ash and finding how much of 
a standard sample of ultramarine must be mixed with this to 
produce the depth of color shown by the ash. 

Microscopical Examination. — The study of the fibres used in 
paper-making can only be conducted by the aid of a good micro- 
scope, and a working knowledge of the instrument can be put to 
practical use in many ways by the paper-maker. The value of 
any particular microscope depends mainly upon the excellence 
of the lenses, but the purchaser should also have regard for the 
steadiness, ease of adjustment, and simplicity of construction of 
the stand. For present uses the preference should be given to an 
instrument having a short tube and low stand. Magnifying powers 
ranging from 70 to 500 diameters may be secured by the combina- 
tions of two eyepieces and two objectives, while in general one 
objective, giving with the eyepiece an enlargement of 70 diameters, 
will be found sufficient for most examinations. Low powers 
which bring out the details wanted are to be preferred to higher 
ones. 

The sample for microscopical examination is prepared by cutting 
a few square inches from different portions of the sheet and 
tearing the pieces into little bits. These are boiled for about 
fifteen minutes in a 1 per cent, solution of caustic soda. The 
whole is then poured upon a sieve having a mesh which is at 
least as fine as 100 to the inch, and the paper which remains upon 
the sieve is gently rubbed with the finger to separate the fibres. 
To complete the separation, the pulpy mass is transferred to a 
bottle with a few garnets or bits of glass and sufficient water 



442 THE CHEMISTRY OF PAPER-MAKING. 

to about half fill the bottle. The bottle is shaken vigorously 
until all lumps are broken up and the material brought to about 
the consistency of stuff as it flows onto the paper machine. 

The only way by which the student can fit himself for the 
microscopical examination of papers is by the careful study and 
comparison under the microscope of slides prepared from known 
samples of the different pulps and fibres and standard admix- 
tures of them. Various standard papers in which the proportions 
of the different fibres are stated are made in Germany for use in 
this work, but it is safer to make up in the laboratory the different 
mixtures from the pulps and to preserve them for use as needed. 
Following the method given above for preparing paper samples 
for examination, the student should first prepare a set of stan- 
dards from — 

1. Pure liuen paper. 

2. Pure cotton rag paper. 

3. Bleached soda poplar fibre. 

4. Bleached sulphite spruce. 

5. Unbleached sulphite spruce. 

6. Bleached straw fibre. 

7. Bleached esparto fibre. 

8. Half-bleached jute 

9. Ground wood (spruce). 
10. Ground wood (poplar). 

After being properly pulped, the samples should be put in 
small bottles of uniform size and shape and marked with the 
number of the sample on a small label on the bottom of the 
bottle. There should then begin a thorough and systematic 
examination of slides made from the different samples, until the 
characteristics of each pulp become familiar. Attention should 
be paid not only to the length and relative diameter of the fibres, 
but to the thickenings and markings of the cell-wall and to 
characteristic cells, not fibres, which are found in the pulp. A 
frequent reference to Plate 1, and to the text in the chapter on 
Fibres will be found useful. 

Besides the physical features above referred to, and upon which 
the main reliance must be placed for the recognition of the dif- 
ferent fibres certain distinctive differences appear when the fibres 
are subjected to the action of various staining agents. The brown 
coloration noticed when a streak is made with nitric acid upon 



PAPER-TESTING. 443 



paper containing ground wood or other lignified fibre gives a rough 
example of the action of such a staining agent. Under the micro- 
scope similar methods of staining may be applied with sufficient 
refinement to permit of a rough classification of the different sorts 
of fibres by means of the colors which are thus developed. The 
most important of these reagents are — 

1. Iodine Solution. — Made by dissolving 1 gramme of iodine 
and 5 grammes of potassium iodide in 100 c.c. of water. This 
solution is used alone or in connection with 

2. Sulphuric Acid. — The acid is prepared of proper strength 
by mixing carefully, in order to avoid sudden heating, three volumes 
of sulphuric acid of specific gravity 1.84 with one volume of dis- 
tilled water and two volumes of pure glycerine. It is ready for 
use when it has become cool. 

3. Aniline Sulphate. — A saturated solution of the salt in alco- 
hol. This stains ground wood and other lignified fibres yellow. 

If, after being thoroughly beaten up and separated, a small quan- 
tity of the paper to be examined is placed on the slide with a drop 
of iodine solution, it will be found that the fibres may be grouped 
as follows according to the staining action of the iodine upon 
them : — 

1. Colorless Fibres. — Bleached chemical wood fibre, bleached 
straw, and esparto. 

2. Fibres ivhich are stained Yellow. — Ground wood and jute. 

3. Fibres which are stained Brown. — Cotton, linen, hemp. 

The use of iodine in the identification of the different fibres may 
be further extended if the iodine is employed in connection with 
the diluted sulphuric acid above mentioned. In this case the 
iodine is allowed to act for a few minutes upon the fibres on the 
slide, and the excess of reagent is removed by carefully pressing 
down upon them a small square of blotting-paper. This is raised 
without disturbing the fibres, and after a drop of the diluted acid 
has been deposited upon them the preparation is covered with a 
thin cover-glass. The staining effects thus developed are not the 
same as those due to the action of the iodine alone, and are those 
to which occasional reference was made in the chapter on Fibres. 

Thus treated, fibres which consist of pure cellulose, like cotton, 
bleached linen, straw, esparto, and wood take on a color which 
may, in case of the different fibres, range from pure blue to purple 
or even to red slightly tinged with blue. Jute, ground wood. 



444 THE CHEMISTRY OF PAPER-MAKING. 

unbleached and poorly cooked sulphite, and other lignified fibres 
turn deep yellow. The staining also brings out more clearly those 
differences in structure which aid in the recognition of the fibres. 

Aniline sulphate solution stains the lignified fibres yellow, and 
is especially useful for bringing ground wood into prominence. 

Another very delicate reagent for detecting the presence of 
ground wood is phloroglucin. It is employed in solution prepared 
by dissolving 2 grammes of the reagent in 25 c.c. of alcohol and 
adding 5 c.c. of concentrated hydrochloric acid. It stains lig- 
nified fibres a brilliant red. 

When the student has familiarized himself with the microscopi- 
cal appearance of the standard samples, bottles should be selected 
at random from the set and examined until without reference 
to the number he finds himself able to identify any sample. 
Standard mixtures should then be prepared by weighing off and 
mixing the air-dry fibres in definite proportions and reducing to 
pulp as in case of paper. The following forms a convenient set of 
such mixed standards with which to begin : — 

1. Linen 50 per cent., cotton 50 per cent. 

2. Cotton 30 per cent., bleached poplar fibre 70 per cent. 

3. Bleached sulphite spruce 30 per cent., bleached poplar 70 per 

cent. 

4. Cotton 10 per cent., bleached sulphite spruce 20 per cent., 

bleached poplar 70 per cent. 

5. Unbleached sulphite spruce 70 per cent., jute 30 per cent. 

6. Unbleached sulphite spruce 50 per cent., spruce ground wood 

50 per cent. 

7. Unbleached sulphite spruce 50 per cent., poplar ground wood 

50 per cent. 

8. Unbleached sulphite spruce 20 per cent., spruce ground wood 80 

per cent. 

9. Unbleached sulphite spruce 20 per cent., poplar ground wood 

80 per cent. 

10. Bleached poplar 50 per cent., bleached straw 50 per cent. 

11. Bleached straw 50 per cent., bleached esparto 50 per cent. 

Besides enabling one to determine the proportions in which 
the different fibres are present in a paper, the microscope will 
also yield considerable information as to the manner in which 
these have been beaten. The action of a refining engine like the 
Jordan breaks or cuts many of the fibres, and leaves the ends 



PAPER-TESTING. 445 



blunt. Long beating in the common beating engine, on the other 
hand, breaks up the ends into little tendrils which curl off in 
every direction, and are often quite separated from the original 
fibre. If the fibres of one sort are found in this last condition, 
while the other fibres are nearly whole or broken sharply across, 
it is safe to assume that the much broken stock was put into the 
engine first and given a preliminary beating before the addition 
of the rest of the furnish. 

Determination of Ground Wood. — Various qualitative methods 
of extreme delicacy have been worked out for the detection of 
ground wood in paper which do not require a resort to the micro- 
scope. The well-known nitric acid test, which consists merely in 
making a streak upon the paper with concentrated nitric acid, and 
noting whether the brown color which indicates the presence of 
uncooked wood is developed, is the test most frequently employed 
outside of laboratories. 

A solution of aniline sulphate, prepared after the manner already 
described, is one of the best reagents for the detection of ground 
wood. If the paper is dipped in the solution and then allowed to 
dry, any ground wood which may be present is stained yellow, and 
from the depth of color thus obtained a rough idea may be 
formed of the proportion in which ground wood enters into the 
composition of the sheet. 

Phloroglucin may be used either in the acid solution previously 
mentioned, or the paper may first be dipped in dilute hydrochloric 
acid, then dried and wet with a solution of phloroglucin in alcohol. 
The pink or red coloration due to liquefied tissues is very charac- 
teristic, and the depth of color may serve here, as in case of aniline 
sulphate, to give an approximation to the quantity of ground wood 
in the paper. 

It should be noted in connection with these tests, that what they 
really indicate is the presence of lignified fibre, and that this is not 
necessarily present in the condition of ground wood. Jute, for 
instance, gives a brilliant yellow with aniline sulphate, and sulphite 
fibre which has not been thoroughly reduced responds similarly to 
the reagent. 

It has, moreover, been pointed out by F. v. Hohnel, that various 
carbohydrates, such as cane sugar, dextrins, etc., give reactions 
resembling the lignin reactions ; for instance, Swedish filter 
paper, prepared from pure cellulose, impregnated with cane-sugar 



446 THE CHEMISTRY OF PAPER-MAKING. 

solution and tested with phloroglucin and hydrochloric acid at first 
gave no reaction, but when dry it becomes distinctly red just as 
if wood fibre were present. Again, wood cellulose, which tested in 
the ordinary way with phloroglucin and hydrochloric acid, showed 
only traces of lignin, became intensely red when, after treatment 
with the reagents, it was washed slightly and then quickly dried 
at 100°-110° C. 

For these reasons the only conclusive evidence of the presence 
of ground wood is that furnished by the microscope. The fibre 
bundles which always occur in ground wood, and which are 
characterized by their broken ends and transverse markings, are 
then easily recognized. A surprisingly large proportion of the 
fibres are, however, well separated and unbroken, but these with 
the bundles stand out prominently when the material on the slide 
has first been stained with aniline sulphate. 

A few chemical methods for the quantitative determination of 
ground wood have been proposed, but are rarely employed, as they 
entail more work than the matter usually warrants, while they are 
not much more accurate than a careful microscopical examination 
which gives an approximation sufficiently close for most practical 
purposes. 

The most satisfactory of these chemical methods is that of 
Godeffroy and Coulon, which depends upon the fact that lignified 
wood fibre has the property of reducing gold from a solution of 
gold chloride while the purer forms of cellulose which constitute 
cotton, linen, chemical wood, straw, and similar fibres, do not have 
this power. The present method as simplified and otherwise 
improved by Godeffroy is as follows : — 

Two equal portions of the paper are taken, and both are boiled 
for ten minutes in 10 per cent, aqueous ammonia, then thoroughly 
washed and dried. One portion is burned, and the ash determined. 
The other portion is boiled for ten minutes with a solution of gold 
chloride, then removed, washed, dried, and burned. From the 
weight of ash obtained, that found in the untreated paper is 
deducted, giving the weight of gold, which multiplied by 100 and 
divided by 21.2 gives the percentage of lignocellulose in the paper. 
The factor 21.2 represents the quantity of gold which 100 parts 
of ground wood will reduce under these conditions as determined 
by numerous experiments. 

Testing Pulp for Moisture. — The determination of the amount 



PAPEB-TE STING. 447 



of moisture in a given sample of pulp or paper is a very simple 
operation, as will appear from the method given below. The great 
chance for error lies in the manner in which the sample is drawn, 
and here too much care cannot be exercised. The following 
methods of sampling are those used in our own work, and long 
experience has shown us that they give a sample which fairly and 
accurately represents a lot of pulp. 

If the pulp is coming from the machine, a uniform strip 2 
inches wide should be taken every twenty minutes across its entire 
width. If the pulp is received at the mill in bales, and if these 
can be opened without too great inconvenience, one bale in ten 
should be taken at random from the lot and opened ; from a sheet 
at about the centre of one of these bales a strip 1^ inches wide is 
cut across the width of the sheet. A similar strip is cut from the 
fifth sheet of the next bale. The strip from the third bale is cut 
from the centre, but this time lengthwise of the sheet. The sample 
from the fourth bale is taken from the fifth, as is the case of the 
second bale, but lengthwise. The whole number of bales set aside 
for sampling — that is, one bale in every ten in the lot — is then 
sampled in this order. 

For sampling pulp on dock, or where for many reasons it is 
impossible to open the bales, we employ a special tool similar to 
a washer cutter, but with a heavier and longer blade. This tool 
is used with a bit-stock, and enables the sampler to easily cut 
through 25 or 50 sheets, removing from each a disk 3 inches in 
diameter. The sampler first cuts through the bagging around the 
bale with a knife, and, if the pulp is fairly thick, drives the tool in 
until, on being withdrawn, it will remove 25 or more disks. The 
second, fifth, tenth, fifteenth, twentieth, and twenty-fifth disks are 
taken, and the others replaced in the bale. One bale in every ten 
is sampled in this manner, and, so far as possible, in different places. 
In all cases, and this point is one of the first importance, the 
moment the samples are cut they are at once placed in a tin pail or 
can with tightly fitting cover, which is only removed to admit a 
new portion of the sample. The can with its contents is weighed 
in the laboratory. Then, and not until then, is the pulp removed 
and the can weighed alone. The difference between the two 
weights gives the weight of the sample. 

In sampling ground wood it is sufficient to cut one bale in every 
20. The outside sheet of the first bale is cut, and the centre of 



448 



THE CHEMISTRY OF PAPER-MAKING. 






" ,1 2 ) 



j*y 



*N 



^j^rl 



^Iw" 



the next one, and so on. It is sufficient to take a small triangular 
piece instead of a strip, but care should be taken that the pieces 
are about the same size. 

Some form of water-oven is used for drying the sample ; that is, 
a jacketed oven through which a circulation of air can be main- 
tained. The jacket is about one-third filled with water, which is 
kept at the boiling point by a burner below the oven. In this 

way the pulp is dried at a temperature 
which never exceeds 100° C. The ovens 
are made with several compartments, so 
that no two samples are placed in the 
same compartment. The pulp is allowed 
to dry for at least one day, and is then 
quickly transferred to a tin can, which 
is then covered at once, and weighed as 
soon as cool. The pulp is again trans- 
ferred to the oven, and the can weighed 
in order to determine by subtraction the 
weight of the pulp. A second drying 
for one half day follows ; the pulp is 
again weighed as before. If the loss of 
the weight does not amount to more 
than -^ of 1 per cent, on the weight of 
the original sample, the last weight is 
taken as the bone-dry weight, and when 
subtracted from the original weight of 
the sample gives the weight of the 
water which is then calculated into per- 
centages. Should the difference between 
the two weights be greater than that 
indicated above, the pulp must again 
go into the oven for further drying, until two successive weights 
agree within the limit named. 

A German drying oven which has many points of excellence is 
shown in Fig. 93. The top D may be removed for the introduc- 
tion of the sample into the oven 3, which is surrounded by a water 
and steam jacket, as shown. Around this water-jacket is a space 
with perforations at the top, open to the atmosphere and connected- 
at the bottom by pipes leading to the oven. The air is heated 



J 



1 



'tf&prd 



p 



H* 



Fig. 93. — Drying-Oven. 



during its passage down this space and then passes up through 



PAPER-TESTING. 



449 



the oven to make its escape through pipe K, its course being 
shown by the arrows. The thermometer T is not really neces- 
sary. The dotted lines within the oven indicate a cylindrical 
cage of wire gauze into which the pulp may be placed. The 
Knofler oven, shown in Fig. 94, is a 
very convenient form, and is so ar- 
ranged that the weight of the pulp may 
be read off at any time. It is quite 
easy to determine when the pulp has 
become quite dry and to avoid over- 
heating. It consists of a cylinder with 
a tightly fitting cover, and provided on 
the outside with a water gauge and a 
faucet, as shown. Space for the pulp 
in the oven proper is formed by two 
smaller cylinders concentric with the 
first ; the innermost or third cylinder is 
open at the bottom and closed at the 
top so as to form a cylindrical steam 
chamber, the bottom of which is sealed 
by the water. A small pipe connects 
the top of this space with the upper 
portion of the second steam space out- 
side the oven proper. The second 
cylinder projects down as far as the 
bottom of the innermost one, and the 
two are there joined. A section across 
the oven shows it therefore to be ring- 
shape, and by this shape the heating 
surface is enlarged. If pulp is to be 
dried, it is placed in the space between 
the two parts of the wire gauze cage 
shown in Figs. 95 and 96. This is sus- 
pended from a balance beam as shown 
in Fig. 94. If the material to be dried 

is a powder, the cage is replaced by the series of trays in Fig. 97. 

Moisture in " Air-dry " Pulp. — This is usually determined by 

first drying the pulp to constant weight at the temperature of 

boiling water, and then allowing the sample to remain exposed to 




Fisc. 94. 



Knofler Drying- 
Oven. 



the air at the ordinary temperature for twenty-four or forty-eight 



450 



THE CHEMISTRY OF PAPER-MAKING. 







.-, 



Figs. 95-96. — Cage for Hold- 
ing Sample. 



hours, in order that it may take up what is supposed to be the 
amount of moisture normally present in the sample under ordinary 
atmospheric conditions. It is hardly necessary to point out that 

as atmospheric conditions are con- 
stantly subject to variation over wide 
ranges of temperature and humidity, 
there is really no such thing as a 
normal amount of moisture for any 
given sample of pulp or paper. The 
moisture in the sample is at all times 
varying with the atmospheric condi- 
tions, and these are never precisely 
the same in two places at once. The 
impossibility which thus arises of stat- 
ing with- any definiteness what "air- 
dry " pulp really is, makes the air-dry 
basis a most unsatisfactory one for 
sales, and is a source of constant dis- 
pute between buyer and seller. 

Many attempts have been made by 
chemists associated with the paper trade in this country and 
abroad to put the matter on a more definite, and therefore more 
satisfactory, basis. The experiments of Martin L. Griffin are of 
especial value, because of their large number and the 
length of time which they cover. These experiments 
were carried on for several years. During the year 
1884, 10 samples of soda poplar fibre previously 
dried at 212° F. were exposed each day in a room 
having windows open and with no fire. The aver- 
age gain in weight during the year amounted to 6.38 
per cent., which represents the increase due to the 
absorption of the so-called atmospheric moisture. 
During 1886, from 3 to 5 samples previously dried 
as before, were exposed daily in a well-aired brick 
storehouse with cellar and good floor and allowed 
to remain there for a week. The monthly average 
which showed the greatest gain in weight was in 
November, when the moisture absorbed amounted to 9.39 per cent. 
The lowest was in June, when the gain was 5.40 per cent. The 
average gain for the year was 7.04 per cent. The method of test- 




Fig. 97. 



PAPER-TESTING. 451 



ing employed during the year 1888 was somewhat different, and 
consisted in keeping 20 samples in a sheet-iron closet so arranged 
that neither rain or snow could enter, although it permitted circu- 
lation of air. The samples were weighed each day and the fluc- 
tuations in moisture noted. The samples were changed about 
once in three months. The amount of moisture present ranged 
from 9.21 per cent, in November and December down to 5.66 per 
cent, in the previous January. The average for the year was 
7.40 per cent. 

Gemmell, in England, finds as the result of comparatively few 
experiments, that about 10 per cent, of moisture is absorbed. The 
Norwegian pulp-makers claim as much as 12 per cent. 

Two ways of meeting the difficulty which arises from these 
variations have been proposed. The most logical one is, that pulp 
should be bought and sold upon the bone-dry basis, with no 
allowance for atmospheric moisture. This,, of course, means a 
readjustment of prices to meet the new conditions of sale. The 
other and most generally adopted plan is for the buyer and seller 
to fix upon, by agreement, some arbitrary percentage which shall 
represent the air-dry moisture in the pulp. As a result of the 
experiments of Dr. Norton, 8 per cent, is commonly taken in case 
of ground wood ; that is, 92 lbs. of the bone-dry pulp are said 
to represent 100 lbs. of the same pulp in the air-dry state. 
Soda pulp is commonly sold on the basis of its cariying 7.50 per 
cent, of atmospheric moisture, while in case of sulphite fibre the 
figure usually recognized by the trade is 10 per cent. 

Where such a basis has been accepted, the method of figuring 
air-dry pulp is as follows : The sample is first made bone-dry by 
drying in a water oven to constant weight. The loss in weight 
represents the moisture in the sample, and is calculated into per 
cents.; this figure, subtracted from 100, gives the per cent, of 
absolutely dry fibre. If now the pulp were sold on 10 per cent, 
basis, every 90 parts by weight of the bone-dry pulp represents 100 
parts of air-dry. If the basis is 8 per cent., 92 parts of bone-dry 
pulp are required to make 100 of air-dry, while on the basis of 7.50 
per cent., 92.50 parts of the dry pulp are required to make 100 of 
the air-dry. The percentage of bone-dry fibre found is, therefore, 
divided by 90 or 92 or 92.50, as the case may be, and the quotient 
multiplied by 100, the product being the percentage of air-dry pulp 
on the basis taken. 



452 THE CHEMISTRY OF PAPER-MAKING. 



CHAPTER X. 

ELECTROLYTIC PROCESSES. 

At the time electrolytic processes for the production of hypo- 
chlorites were first exploited in the large commercial way it was 
thought that they offered to the paper-maker a direct and simple 
method of preparing at the mill the liquors required for the 
bleaching of the stock, and this on such a basis of economy as to 
make it only a question of time when these so-called processes of 
electric bleaching would supplant the older method, which involved 
the use of chloride of lime. With the prospect that the paper- 
maker would have added to his other duties the superintendence 
of such electrolytic plants, it seemed desirable that a work on 
paper-making chemistry should set forth in some detail both the 
chemical and electrical principles involved in their operation. At 
the present time, however, the state of the art is such as to hold 
out little probability that the electrolytic production of bleaching 
agents will become a department of the paper-maker's work in any 
such general sense as the recovery of soda-ash or the manufacture 
of bisulphite solutions has already done. Any lengthy discussion 
of these electrolytic processes becomes, therefore, somewhat outside 
the scope of the present work, and it is, moreover, true that such 
of these processes as seem most likely to have a practical interest 
from the paper-maker's standpoint, through their probable effect 
upon the future price of bleaching-powder, are now so far from 
their final terms and subject to such rapid development that any 
description of the present forms of apparatus is likely within a 
short time to have only an historical interest. We shall for these 
reasons make no attempt to go into the subject in greater detail than 
to present briefly the more obvious principles which underlie the 
art, together with the general means involved in their application. 

When a current of electricity passes along a metallic conductor, 
various magnetic and heating effects are observed, but the con- 
ductor itself does not apparently suffer change. Liquids, like 
other bodies, vary among themselves in their power to conduct 



ELECTROLYTIC PROCESSES. 453 

electricity; some, like the oils, being among the best insulators, 
while others are excellent conductors, though never in this respect 
comparable to the metals. Those liquids which conduct electricity 
are termed " electrolytes," and it is the peculiarity of electrolytes 
that they suffer decomposition in direct proportion to the amount of 
current passing through them. The results or products of this 
decomposing action of the current are observed at those points 
called " poles" at which the current enters and leaves the liquid, and 
the operation itself is termed " electrolysis." The point or surface 
at which the current enters is called the " anode," and that at which 
it leaves the liquid is called the " cathode. " The liquid or that com- 
ponent of it which is decomposed is, under the action of the 
current, split up into two constituents called "ions," one of which, 
the "anion," is liberated at the anode surface, while the other, the 
" cathion, " is set free at the cathode surface. When, for example, a 
current is passed through slightly acidulated water, the products 
of the changes set up by the current are oxygen, which appears at 
the positive pole, or anode, and hydrogen, which is evolved at the 
negative pole, the cathode. The proportions of each evolved are 
those in which they unite to form the liquid. If the current is 
sent through fused sodium chloride, common salt, the chlorine is 
evolved at the anode, and metallic sodium at the cathode. This 
last is an example of the simplest form of electrolysis in 
which the products obtained are those directly due to the initial 
decomposition set up by the current. The electrolysis of a salt 
in solution is complicated by various secondary reactions which 
may or do take place between the liberated ions and the com- 
ponents of the liquid. If a solution of common salt in water is 
electrolyzed while the solution is at the same time mechanically 
agitated, the primary results of the electrolysis are, as in case of 
the fused salt, metallic sodium and chlorine, but as a result of 
the secondary reactions set up by contact of the liberated ions 
with the liquid the final and visible products are hydrogen, which 
escapes at the cathode, and sodium hypochlorite, which accumu- 
lates in the liquid. 

If the two electrodes are separated by a porous partition, as, for 
example, one of unglazed earthenware, these secondary reactions 
do not go so far, and the final products are hydrogen and caustic 
soda at the cathode, and gaseous chlorine at the anode. Both the 
caustic soda and the hydrogen are, however, the result of secondary 



454 THE CHEMISTRY OF PAPER-MAKING. 

action between the metallic sodium originally set free and the 
water. The quantity of an electrolyte decomposed by the passage 
through it of a given quantity of electricity is always the same, 
but the course of the secondary reactions, and therefore the nature 
and quantities of the various final products, may be greatly modi- 
fied by such conditions as the temperature and concentration of the 
solution, the size and character of the electrodes, and the strength 
of current. For these reasons, when a given product is desired, 
there may be, as the conditions of the work vary, corresponding 
variations in the quantity of the desired product obtained. The 
quantity found, divided by the theoretical amount, gives what is 
called the " current efficiency " of the process or apparatus. 

In electro-chemical work, as in other departments of electricity, 
certain units are employed for measuring and expressing the 
strength and energy of the current, the resistance of the circuit 
around which it flows, and the power of the electromotive force. 

As water, when in motion, possesses energy, while it would not 
when at rest and free from strain be said to have energy or be 
force, so electricity, though not to be regarded as a form of force 
or energy, possesses energy when in motion and will do work. 
Electricity in locomotion, or the electric current, presents many 
analogies to flowing water. They are crude analogies and must 
not be pushed too far, but bearing this in mind they may be safely 
used to obtain a clearer insight into the meaning and relations of 
common electrical terms. When water is pumped or carried from 
the ^ea-level to a higher one, a certain amount of work is done, 
and by virtue of its new position the water has an equal amount 
of potential energy, which reappears when the water is returning 
to the level from which it came. A difference of head is created, 
and the resulting pressure causes the water to flow. So, by 
properly directed work, what may be called a difference of electri- 
cal level may be set up, and this difference is termed a " difference 
of potential." Electricity tends to flow from a point of high 
potential to a point of low potential, and that which produces this 
tendency, or which causes electricity to flow, is known as "electro- 
motive force," more briefly written E. M. F. The measure of 
electromotive force is the" volt." The E. M. F. set up by an ordi- 
nary Daniell's cell, such as is used in telegraphing, is, roughly 
speaking, one volt. The measure of the quantity of electricity 
which flows is the "ampere." The measure of the resistance or 



ELECTROLYTIC PROCESSES. 455 

opposition to its flow which the electric current encounters more 
or less in all conductors is the "ohm." It is the resistance of a 
column of pure mercury having a cross-section of one square milli- 
metre and 106 centimetres long. One mile of ordinary telegraph 
wire has a resistance of about ten ohms. An E. M. F. of one volt 
will send a current of one ampere through a resistance of one ohm. 
Electricity always flows in a closed circuit, the same quantity 
of electricity passing any cross-section of the circuit in the same 
time. The quantity of electricity which flows, measured in 
amperes, is equal to the E. M. F. in volts divided by the resistance 
of the circuit in ohms. This statement of the fact is known as 

Ohm's Law, and it expressed in the formula C=—, in which 

It 

C=the current in amperes, 2?= the electromotive force in volts, 
and i2 = the resistance of the circuit in ohms. 

Small currents moving under a high electromotive force, and 
consequently through much resistance, are sometimes spoken of 
as intensity currents, while larger currents under a low electro- 
motive force and through low resistance are sometimes called 
quantity currents. A small stream of water under great pressure 
will do as much work as a larger stream under correspondingly 
lower pressure, and so a small quantity of electricity propelled by 
a high electromotive force will do as much work as a much 
greater quantity moving under a proportionately lower E. M. F. 
The energy or power of the current in doing work is measured in 
"watts"; a current of one ampere under an E. M. F. of one volt has 
an energy of one watt. Seven hundred and forty-six watts are 
equal to one horse-power. The power of a circuit in watts is 
equal to the product of the number of amperes flowing multiplied 
by the E. M. F. in volts. The most efficient dynamos now in use 
generate a current having a power of about 680 watts for each 
horse-power at the dynamo pulley. 

The points or terminals of a battery or dynamo to which the ends 
of the external circuit are joined are termed poles, the point of 
high potential, from which electricity flows into the circuit, being 
called the positive or + pole, while the point of low potential 
toward which electricity flows is known as the negative or — pole. 
A current is said to be continuous when it is flowing in one direc- 
tion; when the relation of the poles, and consequently the direc- 
tion of flow, is subject to rapid reversals, the current is said to be 



456 THE CHEMISTRY OF PAPER-MAKING. 

an alternating one. The ordinary rate of reversal in commercial 
alternating currents is 120 times per second. At present the 
continuous current is the only one which is adapted for electro- 
chemical work. 

The theory of electrolysis is roughly this : It is assumed, and 
the assumption is justified by many experimental facts, that in all 
liquids which conduct electricity there is not only an incessant 
movement of the molecules of the liquid, but that probably, by 
virtue of this motion, certain of the molecules are split up into 
their component atoms, and that these free atoms, or ions, are 
moving about in every direction throughout the liquid, combining 
with other atoms as they come within the sphere of each other's 
attractive force, and again splitting up and recombining. Under 
ordinary conditions, when no current is passing, the motion of the 
ions may be in any direction, but under the influence of the 
current an attractive force comes into play which impels the ions 
toward one electrode or the other, according as they are positively 
or negatively charged. 

Although as a laboratory experiment it has been for many years 
an easy matter to decompose solutions of the chlorides, with pro- 
duction of hypochlorite solutions or of free caustic and gaseous 
chlorine, the practical difficulties in the way of commercial opera- 
tion have been very serious. It is necessary that the electrodes 
should have large surfaces and be near together, in order to cut 
down the resistance of the electrolyte to the lowest possible point, 
since that portion of the energy of the current spent in overcoming 
this resistance is wasted. For the same reason, if a diaphragm is 
used, it must be of such a nature as to be efficient in preventing 
diffusion and yet of low resistance, and the two qualities are in a 
measure contradictory. The chlorine and oxygen liberated at the 
anode have a powerfully corrosive action upon nearly all sub- 
stances, and yet the anode must not be appreciably attacked, for 
the double reason that just so far as it is attacked the products of 
the electrolysis and the anode itself are lost. 

In spite of these difficulties there has been within the last few 
years a great advance in the methods of commercial electrolysis, 
and especially in those having for their object the decomposition 
of chlorides. The number of these processes at the present time 
is large, and certain of them have unquestionably advanced beyond 
the experimental stage. 



ELECTROLYTIC PROCESSES. 



457 



The first electrolytic process to be seriously considered by 
paper-makers was that of Hermite, although Becquerel, in 1843, 
noted that chlorine and soda are the products of the decomposition 
of salt, while Brandt, in 1848, claimed to have suggested as early 
as 1820 the application of electrolyzed sea-water to bleaching. 
Charles Watt, working with Hugh Burgess, was probably the first 
to demonstrate experimentally the possibilities of the method, but 
the crude means then available for generating the necessary cur- 
rent precluded any commercial development. The results of his 
researches are embodied in British patent No. 13,755, a.d. 1851. 

Following Watt came numerous other experimenters, until in 
1886 Hermite brought forward a well-considered system for the 




Fig. 



Hermite Electkoltzer. 



production of hypochlorite of magnesia, by electrolysis of a 5 per 
cent, solution of the chloride. 

Hermite 's apparatus consists of a dynamo capable of supplying 
a current of about 1250 amperes, one or more electrolyzers, a 
storage tank for liquor, the necessary pumps and piping for circu- 
lation, and two or more chests for holding the pulp to be bleached, 
and fitted with agitators. The electrolyzers, Fig. 98, consist of 
galvanized cast-iron boxes, having at the bottom a perforated pipe 
fitted with a cock, through which a 5 per cent, magnesium chloride 
solution is admitted from the storage tank to the electrolyzer ; the 
top of each box is surrounded by a channel in which the solution 
is received on overflowing the sides of the box ; from this channel 
it is carried away by a pipe, thus keeping up a continuous circu- 
lation. The negative electrodes are shown in the figure, and 



458 



THE CHEMISTRY OF PAPER-MAKING. 




Fig. 99. — Positive Plate. 



consist of a number of zinc discs arranged upon two spindles, 
which are caused to revolve slowly by means of worms and wheels. 
Between each of these discs is placed a positive plate, of which a 
view is shown in Fig. 99. The active surface of the plates is 

formed of platinum gauze, mounted in a 
frame of ebonite to give it stiffness, and 
each plate is connected to the copper 
casting shown above the box by means 
of a stud and nut, and can be removed 
at will. The positive terminal of the 
dynamo is connected to this copper cast- 
ing, and the current distributes itself 
over the whole system of platinum plates, 
which thus form one large anode. It 
passes from them through the solution to 
the zinc discs, which form the cathode, 
as they are in contact with the iron 
box to which the negative pole of the dynamo is connected. 
In order to keep the negative plates clean and free from the 
magnesium hydrate which is deposited upon them, flexible knives 
are attached to the ebonite frames of the positive plates, and these 
knives scrape the surface of the slowly revolving zinc discs. 

Several electrolyzers, commonly ten, are generally joined up in 
series, the negative terminal of the first being connected with the 
positive terminal of the second, and so on. 

The solution of magnesium chloride passing into the electrolyzers 
is under the action of the current converted largely into one of 
magnesium hypochlorite, the practical effect of the reactions set 
up by the current being to add an atom of oxygen to the mag- 
nesium chloride molecule. The electrolyzed solution then passes 
directly upon the pulp contained in the first of a series of chests, 
or engines, the pulp in the first chest being that which is most 
nearly bleached. The solution is admitted at the bottom of the 
chest, and passes upward through the pulp, and is removed by a 
washing cylinder and transferred to the second chest. The num- 
ber of such chests in series should be limited by the rate of flow of 
the solution, and the rapidity with which the active chlorine is 
exhausted. Two or three chests are usually sufficient. A small 
amount of soluble organic matter is extracted from the pulp by 
the solution, and as this is of such a nature that it requires a little 



ELECTROLYTIC PROCESSES. 459 

time for its complete oxidation, the liquor passing from the last 
chest into the storage tank should contain a small residuum of 
active chlorine to destroy this dissolved organic matter, which 
would otherwise gradually accumulate in the solution and reduce 
the efficiency of the process. Under conditions properly regulated 
in the manner indicated the bleaching action of the solution is 
extremely rapid, and the pulp is bleached to good color without 
loss of strength. This is true of such refractory fibres as soda 
spruce. 

In the process of bleaching the magnesium hypochlorite is of 
course reduced to the initial magnesium chloride, and the process 
thus involves a complete cycle of changes, in which, theoretically, 
only the coloring-matter of the fibre and the power needed to drive 
the dynamo are consumed. There is of necessity, in practice, a 
small loss of solution which is carried away in the bleached 
pulp. 

Each eiectrolyzer working under this system requires an electro- 
motive force of five volts. Nine or ten electrolyzers and an 
expenditure of about eighty horse-power are required to produce 
daily the equivalent in electrolyzed solution of one ton of bleach- 
ing-powder. 

At the time of its first exploitation the great efficiency of the 
Hermite electrolyzed solution, when used according to his method, 
led to claims that its activity was largely due to the presence of 
new and hitherto unsuspected compounds developed by the elec- 
trolysis. Later experience has shown these claims to be unfounded, 
the superior efficiency of the solution being partly due to the fact 
that hypochlorite of magnesia is in itself a better bleaching agent 
than ordinary bleaching-powder, but still more to the method of 
circulation adopted, by which, as already stated, the fresh and 
strong solution passed directly upon the nearly bleached pulp and 
was finally exhausted by contact with the brown pulp. The solu- 
tion now used by Hermite is practically one of common salt, only 
a small proportion of magnesium chloride being added. His 
process has met with gratifying success in France, but in this coun- 
try and in England it has encountered difficulties which, though 
not inherent in the process, have proved a bar to its introduc- 
tion. 

The present tendency of development is toward those processes 
which have for their object the production of commercial bleach 



460 THE CHEMISTRY OF PAPER-MAKING. 

and alkali, and although certain to effect ultimately a material 
reduction in the price of these staples, they are not likely to 
introduce any radical changes into the chemical operations of the 
paper-mill. The most prominent of these processes are those of 
Greenwood, Andreoli, and Holland and Richardson in England, 
and of Cutten, Crane} 7 , Carmichael, and especially Le Sueur and 
Waite in this country. The fundamental principles underlying 
all these processes are the same, the differences being found in 
the design of the apparatus and in details of work. All of them 
work with saturated brine and employ some form of diaphragm 
between the electrodes to prevent diffusion and consequent recom- 
bination of the chlorine and caustic. Gas carbon has been almost 
universally adopted as the material for the anode, but the design 
and position of the anode and the means employed to secure 
contact with the conductors and to prevent too rapid disintegration 
of the carbon vary in the different processes. Similar variations 
are found in the general arrangement of the decomposing cell, the 
electrodes being sometimes placed horizontally, while in other 
cases, and much more commonly, they stand in a vertical position. 
The cathode is always of iron, although mercury has been proposed 
for certain forms of plant, and consists of a plate, a casting of 
special design, or wire gauze. In addition to variations in the 
material, form, and position of the diaphragm, the processes show 
important differences in the auxiliary means employed to further 
limit the losses caused by diffusion. Perhaps the best of these 
consists in maintaining a flow of the electrolyte through the 
diaphragm, either toward the cathode or to both electrodes. 

Although such differences as have been noted may appear as 
minor ones, they are really what determine the success or failure 
of a process. A cell which requires six volts to send a given 
current through it cannot compete commercially with one which 
as a result of better design requires only four and one-half volts, 
for this apparently slight difference means that the former cell 
requires the expenditure of 33 per cent, more power than the 
latter for a given quantity of product. 

It has been already pointed out that the present rapid develop- 
ment of these processes would soon make obsolete any detailed 
account of the several systems, but keeping in mind the differences 
in detail noted above, the following general description may be 
taken as applying to them all. 



ELECTROLYTIC PROCESSES. 461 

The dynamo for supplying the current is so wound as to deliver 
a continuous current of large volume under moderate voltage. 
One supplying 1250 amperes at 120 volts may be used to advan- 
tage, and requires about 225 horse-power. Large copper conductors 
carry the current to the decomposing cells, which are commonly 
arranged in multiple arc. That is, the cells are arranged in sets, 
the whole current going through each set and on to the next set, 
but only a fraction of the current going through a single cell. 
This fraction varies from 60 to 500 amperes, according to the size 
and construction of the cell, and the number of cells in a set varies 
accordingly. Each cell requires an electromotive force of from 
four and a half to six volts. The cells themselves consist of 
troughs, or vessels, which may be of iron or slate or earthenware, 
but such portions of them as come in contact with the chlorine 
must of course be of a material not corroded by the element, and 
this most commonly is slate or earthenware. Several cells, or at 
least several anode compartments, may open into a common trough, 
or each cell may be self-contained. They differ among themselves 
very much in size, appearance, and construction, but each embodies 
three essential elements, — an anode of gas carbon, a diaphragm or 
its equivalent, and an iron cathode. The whole cell is filled to 
such a point with saturated brine that both anode and cathode, 
with of course the diaphragm between them, are immersed in 
the liquid. 

The current enters the cell through the conductor connected 
with the anode, and from the anode passes through the brine and 
the saturated diaphragm to the cathode, where it makes its exit by 
another conductor. The chlorine evolved at the anode leaves the 
liquid, and being confined by the walls of the anode compartment 
passes off into pipes leading to absorption chambers containing 
lime, or, if a solution is wanted for use at once, into agitating 
apparatus containing milk of lime. The hydrogen liberated at 
the cathode either passes off directly into the air, or the construc- 
tion of the apparatus may be such that it is confined until it makes 
its way out through pipes. The caustic soda formed on the 
cathode by reaction of the water with the metallic sodium set free 
by the current gradually accumulates in the liquid, and either 
flows off automatically as a strong solution or is drawn off from 
time to time, either for use directly or for concentration by heat 
in order to separate the accompanying salt by crystallization and 



462 THE CHEMISTRY OF PAPER-MAKING. 

to secure the solid hydrate. Such plants have shown in practice 
an efficiency ranging, according to their type, from 50 to 90 per 
cent, of the theoretical, or, in other words, have produced from 
18.12 grammes to 32.62 grammes of caustic, and from 16.08 
grammes to 28.94 grammes of chlorine per ampere day, the the- 
oretical yields being 36.24 grammes of caustic and 32.16 grammes 
of chlorine. 



APPENDIX. 



APPENDIX. 



3XKC 



RULES FOR THE SPELLING AND PRONUNCIATION OF 
CHEMICAL TERMS. 

Adopted by the American Association for the Advancement of Science in 1891. 

GENERAL PRINCIPLES OP PRONUNCIATION. 

1. The pronunciation is as much in accord with the analogy of the English 
language as possible. 

2. Derivatives retain as far as possible the accent and pronunciation of the 
root word. 

3. Distinctly chemical compound words retain the accent and pronunciation 
of each portion. 

4. Similarly sounding endings for dissimilar compounds are avoided (hence 
-id, -ite). 

ACCENT. 

In polysyllabic chemical words the accent is generally on the antepenult ; in 
words where the vowel of the penult is followed by two consonants, and in all 
words ending in -ic, the accent is on the penult. 

PREFIXES. 

All prefixes in strictly chemical words are regarded as parts of compound 
words, and retain their own pronunciation unchanged (as d'ceto-, d'mido-, d'zo-, 
hy'dro-, i'so-, nl'tro-, nitro'so-). 

ELEMENTS. 

Iii words ending in -ium, the vowel of the antepenult is short if i (as 
iri'diuin), or y (as didy'mium), or if before two consonants (as cd'lcium), but 
long otherwise (as titd'nium, sele'nium, cliro' miuni) . 



alu'minum 


cd'dmium 


co'balt 


germd'nium 


iron 


a'ntimony 


cd'lcium 


colli' mbium 


glu'cinum 


la'nthanum 


a'rsenic 


ca'rbon 


co'pper 


gold 


lead 


bd'rium 


ce'rium 


didy'mium 


hy'dro gen 


li'thium 


bi'smuth (biz) 


cossium 


e'rbium 


i'ndium 


magne'sium (zhium) 


bo'ron 


chid' r in 


fu'orin 


i'odin 


ma'nganese (eze) 


bro'min 


chro'mium 


(jd'llium 

465 


iridium 


mefrcury 



466 



THE CHEMISTRY OF PAPER-MAKING. 



molybdenum plWtinum sele'nium tellu'rium ura'nium 

nVckel potd'ssium si'licon te'rbiu)n vdna'dium 

nl'trogen rho'dium silver thd'llium ylte'rbium 

o'smium rubi'dium so'dium tlio'rium y'ttrium 

o'xygen ruthe'nium strontium (shium) tin zinc 

palla'dium sama'rium su'lfur titd'nium zirco'nium 

phos 1 phorus scd'ndium ta'ntalum tu'ngsten 

Also : ammo'nium, phospho'nium, lid'logen, cyd'nogen, dmi'dogen. 

Note in the above list the spelling of the halogens, cesium and sulfur ; f is used 
in the place of ph in all derivatives of sulfur (as sulfuric, sulfite, sulfa-, etc.). 

TERMINATIONS IN -iC. 

The vowel of the penult in polysyllables is short (as cyd'nic, fumd'ric, arse'nic, 
sili'cic, lo'dic, buty'ric), except (1) u when not used before two consonants (as 
mercu'ric, pj-u'ssic), and (2) when the penult ends in a vowel (as benzo'ic, ole'ic) ; 
in dissyllables it is long except before two consonants (as bo'ric, cl'tric). Excep- 
tion : ace'tic or ace' tic. 

The termination -ic is used for metals only where necessary to contrast with 
-ous (thus avoid aluminic, amnionic, etc.). 

TERMINATIONS IN -OUS. 

The accent follows the general rule (as jild'tinous, su'lfurous, pho'spliorous, 
coba'ltous). Exception: ace' tons. 

TERMINATIONS IN -ate AND -ite. 

The accent follows the general rule (as d'cetdte, va'nadate) ; in the following 
words the accent is thrown back, d'bietdte, a'lcoholate, a'cetonate, d'ntimomte. 

TERMINATIONS IN -id (FORMERLY -ide). 

The final e is dropped in every case and the syllable pronounced id (as 
chlo'rid, I'odid, hy'drid, o'xid, hy'droxid, su'lfld, a'mid, a'nilid, mure'xid). 



terminations in -ane, -ene, -ine, and -one. 

The vowel of these syllables is invariably long (as me'thdne, e'thdne, na'ph- 
thalene, a'nthracene, pro'pine, qui'none, a'cetone, ke'tone'). 

A few dissyllables have no distinct accent (as benzene, xylene, cetene). 

The termination -ine is used only in the case of doubly unsaturated, hydro- 
carbons, according to Hoffmann's grouping (as proplne) . 

TERMINATIONS IN -in. 

In names of chemical elements and compounds of this class, which includes 
all those formerly ending in -ine (except doubly unsaturated hydrocarbons) the 
final e is dropped, and the syllable pronounced -in (as chlo'rin, brd'min, etc., 
d'min, d'nilin, mo'rphin, qui'nin (kwi'mn), vani'llin, alloxd'ntin, absi'nthin, emu'lsin, 
cd'ffevn co'cain). 



APPENDIX. 467 



TERMINATIONS IN -Ol. 

This termination, in the case of specific chemical compounds, is used exclu- 
sively for alcohols, and when so used is never followed by a final e. The last 
syllable is pronounced -51 (as gly'col, phe'nol, cre'sol, thy'mol (ti), gly'cerol, qui'nal. 
Exceptions : alcohol, a'rgol. 

TERMINATIONS IN -Ole. 

This termination is always pronounced -ole, and its use is limited to com- 
pounds which are not alcohols (as i'ndule). 

TERMINATIONS IN -yl. 

No final e is used ; the syllable is pronounced -yl (as a'cetyl, a'myl, ce'rotyl, 
ce'tyl, e'thyl). 

TERMINATIONS IN -yde. 

The y is long (as ci'ldehyde). 

terminations in -meter. 

The accent follows the general rule (as hydro' meter, baro' meter, lactometer). 
Exception : words of this class used in the metric system are regarded as com- 
pound words, and each portion retains its own accent (as ce'ntime"ter, mi'lli- 
me"ter, ki'lome"ter). 

miscellaneous words which do not fall under the preceding rules. 

Note the spelling: albumen, albuminous, albuminiferous, asbestos, gramme, 
radical. 

Note the pronunciation : a'lkallne, a'lloy (n. and v.), a'llotropy, a'llotropism, 
I'somerism, po'lymerism, appard'ius (sing, aud plu.), aqua regia, bary'ta, centigrade, 
concentrated, crystallin or crystalline, electro 1 lysis, liter, mo'lecule, mole'cidar, no'men- 
cld'Hure, ole'fiant, vd'lence, u'nwd"lent, bi'vd"lent, trl' vd" lent, qua' driva!' lent, ti'trate. 

A list of words whose use should be avoided in favor of the 
accompanying synonyms. 

For — Use — 

sodic, calcic, zincic, nickelic, etc. . . sodium, calcium, zinc, nickel, etc., chlorid, 
chlorid, etc. etc. (vid. terminations in -ic, supra). 

arsenetted hydrogen arsin 

antimonetted hydrogen stibin 

phosphoretled hydrogen p>hosphin 

sulfuretted hydrogen, etc. ..... hydrogen sulfid, etc. 

For — Use — For — Use — 

beryllium glucinum furfural .... furfuraldehyde 

niobium colutnbium fucusol .... fucusaldehyde 

glycerin glycerol anisol ..... methyl phenate 



468 



THE CHEMISTRY OF PAPER-MAKING. 



For — Use — 

hydroquinone (and hy- 

drochinon) . . . qulnol 

pyrocatechin .... catechol 

resorcin, etc resorcinol, etc. 

mannite mannitol 

dulcite, etc dulcitol, etc. 

benzol benzene 

toluol, etc toluene, etc. 

ihein caffein 



For — 


Use — 


phenetol . . . 


. ethyl phenate 


anethol . . . 


. methyl allyl phenol 


alkylogens . . 


. alkyl haloids 


titer (n.) . . . 


. strength or standard 


titer (v.) . . . 


. titrate 


monovalent . 


univalent 


divalent, etc. 


. bivalent, etc. 


quaniivalence 


. valence 



Fate, fat, far, mete, met, pine, pin, marine, note, not, move, tube, tub, rule, 
my, y = i. 

' Primary accent; " secondary accent. N.B. — The accent follows the 
vowel of the syllable upon which the stress falls, but does not indicate the divis- 
ion of the word into syllables. 



NEW CELLULOSE DERIVATIVES. 



The chemistry of cellulose has recently been enriched by the dis- 
covery by Cross, Bevan, and Beadle of the remarkable reaction which 
ensues when cellulose (as for example, in the form of bleached poplar 
fibre) is exposed to the action of caustic alkali and carbon bisulphide. 
Many important industrial applications of the discovery have already 
been proposed as the new compound is plastic and soluble in water, 
and yields by its decomposition the original or slightly modified cellu- 
lose which may be thus brought into the form of films, sheets or masses 
without fibrous structure. We quote below from the original paper 
(Jour. Chem. Soc, London, 1893, p. 837). 

Cellulose Thiosulphocarbonic Acid. — When cellulose in any of 
■ its forms is treated with a concentrated solution of sodium hydrate 
(12.5 per cent. Na 2 0), and the alkali cellulose thus obtained is exposed 
to the action of carbon bisulphide vapor, action ensues, and in the 
course of an hour or two a yellowish mass is obtained, which swells up 
enormously on treatment with water, and finally dissolves completely. 
This soluble compound is a cellulose thiocarbonate. 

The action proceeds rapidly when the agents are brought together in 
the ratio — 

C 12 Hn O 10 ; 2 Na 2 ; 2 CS 2 ; 30 to 40 H 2 0. 

The most convenient conditions for laboratory experiment are with the 
alkali in the form of a 15 per cent, aqueous solution of the hydrate 
(11 to 12 per cent. Na 2 0), the proportion by weight of this solution 
being from 3.5 to 4 times that of the cellulose. 



APPENDIX. 469 

The crude solution obtained by dissolving the product in water, and 
containing yellow by-products (trithiocarbonate), yields the cellulose 
derivative in a pure state, on treating it with saturated brine or with 
strong alcohol. It is precipitated by the former in a flocculent con- 
dition, by the latter in leathery masses, which may then be further 
washed with a 13 per cent, solution of sodium chloride or 65 per cent, 
alcohol, respectively. On redissolving in water an almost colorless 
solution of extraordinary viscosity is obtained, which exhibits the 
following properties : — 

(a) Spontaneous Coagulation. — After standing for a period, depend- 
ing on the method of preparation and purification adopted, the solution 
" sets " to a firm coagulum of a hydrated cellulose of the same volume 
as the original solution ; the coagulum then shrinks gradually, becom- 
ing surrounded with a yellow alkaline solution (trithiocarbonate). 
During shrinkage, the cellulose retains the form of the containing 
vessel. 

(6) Coagulation determined by Heat. — The solution may be evapo- 
rated to dryness in thin layers at temperatures not exceeding 50°, 
without sensible decomposition, the dry substance obtained being 
perfectly soluble. 

At 70 to 80°, however, the solution thickens rapidly, and at 80 to 
90° the coagulation is almost instantaneous. These phenomena are 
due to the fact that the compound behaves as a product of association 
of cellulose, alkali, and carbon bisulphide, the coagulation above 
described being a dissociation of the compound into its constituents. 

(c) Coagulation determined by Reagents. — From the foregoing it 
will be evident that the regeneration of cellulose will be determined 
by reagents, reacting either with the alkali or the sulphur group ; 
thus acids and acid salts, sulphites, and metallic oxides all increase the 
rapidity of decomposition. 

Characteristics of the Regenerated. Cellulose. — We have 
assumed that the cellulose is obtained, in the main, unchanged from 
the solution as above described, and this is generally true. It shows a 
general agreement with the normal cellulose in regard to resistance to 
hydrolysis and oxidation, and it follows, from what has been said, that 
it is similar in its capacities for hydration, and also generally in its 
physical properties. 

From the above it appears that carbon percentage is somewhat 
reduced, and it is to be noted also that the attraction of the product 
for moisture is increased, the normal hygroscopic moisture of the 
recovered cellulose amounting to 10 per cent, as compared with 7 per 
cent, in the original cellulose. The original molecule, therefore, 



470 THE CHEMISTRY OF PAPER-MAKING. 

appears to have undergone hydration in the ratio 2 C 12 Ho O 10 H 2 O, and 
we find that, like many other hydrates of the normal cellulose, it gives 
a blue coloration with iodine. 

We have also observed constitutional features differing from those 
of the normal type, as indicated by exceptional behavior in interactions 
such as those which determine solution and the production of the 
ethereal derivatives. 

The constitution of the derivative may, be expressed by the general 

formula CS < ~ , X representing the variable cellulose unit ; that is, 

the acting residue. This is, however, not a cellulose residue pure and 
simple, but an alkali-cellulose, a fact which is to be expected a }->riori, 
and is proved by treating the solution with benzoyl chloride, when 
cellulose is eliminated as a cellulose benzoate. 

The formula, therefore, may be written CS < ~A. , which will 

J SNa 

be seen to be in harmony with the analytical data given above. 

The compound may therefore be described as the sodium salt of 
alkali-cellulosexanthic acid. 

The solutions of the compound give bright yellow precipitates with 
mercury and zinc salts, and a more orange yellow with lead salts. 
Moreover, as stated above, the purified compound in presence of a 
certain quantity of water changes spontaneously into cellulose, alkali, 
and carbon-bisulphide, which confirms this view of its constitution. 
Further, the solutions are precipitated by iodine, the precipitate 
being a thio-derivative which can readily be redissolved with formation 
of the original compound. This action carried out quantitatively 
gives fairly constant numbers. 



APPENDIX. 471 



LIST OF UNITED STATES PATENTS RELATING TO THE 
SULPHITE PROCESS. 

Any of the patents in the following list may be obtained from the 
Patent Office, at Washington, on payment of 10 cents. Coupon books 
containing orders for 50 patents are issued by the office on payment 
of $ 5.00. 
Akin, N. P. 127008. May 21, 1872. 

Manufacture of sulphurous acid. 
Albrecht, J. See Bernard, P. L. 
Archbold, George. 274250. March 20, 1883. 

Manufacture of paper pulp. 
Archbold, George. Reissue, 10328. May 22, 18S3. 

Manufacture of paper pulp. 
Ball, Charles E. 336078. Feb. 16, 1886. 

Digester. 
Biron, Jean B. 67941. Aug. 20, 1867. 

Disintegrating wood to form paper pulp. Claims use of alkaline sul- 
phides and sulphides of lime. Has been cited as anticipating Tilgh- 
man, but does not properly bear upon the sulphite process. 
Bremaker, Charles. 373810. Nov. 29, 1887. 

Digester. 
Bremaker, Charles. 35373. Dec. 7, 1886. 

Digester. 
Bremaker, Charles, and Michael Zier, Sr. 333105. Dec. 29, 1885. 

Digester. 
Briingger, H. 483828. Oct. 4, 1892. 

Digester. 
Briingger, H. 4S3827. Oct. 4, 1892. 

Digester lining. 
Briingger, H. 483826. Oct. 4, 1892. 

Digester lining. 
Burgess, T. P. 432692. July 15, 1890. 

Apparatus for producing bisulphites. 
Carlisle, Frederick. 395691. Jan. 8, 1889. 

Apparatus for absorbing gases. 
Carlisle, Frederick. 284817. Sept. 11, 1883. 

Manufacturing of hydrated sulphurous acid. 
Catlin, Charles A. 366153. July 5, 1887. 

Sulphite solution for wood pulp. 
Catlin, Charles A. 407818. July 30, 1889. 

Process of charging liquids with gas. 
Clamer, Francis J. 283077. Aug. 14, 1883. 

Treating lead to impart to it the property of adhering to other metals. 
Clapp, Eugene H. 305740. Sept. 30, 1884. 

Digester- and valve. Especially applicable to soda process, but valve is 
of interest. 



472 



THE CHEMISTBY OF PAPER-MAKING. 



April 13, 1886. 
July 16, 1889. 
April 13, 1886. 
Nov. 8, 1892. 



339975. 



485809. Nov. 8, 1892. 



485810. Nov. 8, 1892. 



484999. Oct. 25, 1892. 



485000. Oct. 25, 1892. 



Closs, Gotthold. See Schnurmann. 
Comstock, W. O. 453076. May 26, 1891. 

Digester lining. 
Cornwell, C. 432604. July 15, 1890. 

Apparatus for producing bisulphites. 
Crocker, William 0. and William P. 339974. 

Producing sulphite or bisulphite of soda. 
Crocker, William O. and William P. 406886. 

Digester. 
Crocker, William O. and William P. 

Process of making bisulphites. 
Curtis, C, and N. M. Jones. 48580S. 

Digester. 
Curtis, C, and N. M. Jones. 

Digester. 
Curtis, C, and N. M. Jones. 

Digester. 
Curtis, C, and N. M. Jones. 

Digester. 
Curtis, C, and N. M. Jones. 

Digester. 
Denton, A. A. 339387. April 6, 1886. 

Apparatus for exposing large surfaces of liquid to air, or vapor, or gas. 
Drewsen, V. 492196. Feb. 21, 1893. 

Recovery of gas. 
Eaton, A. K. 119224. Sept. 26, 1871. 

Use of sulphite of sodium as a solvent in reducing wood to fibre. 
Ekman, Carl D. 253357. Feb. 7, 1882. 

Treating wood. 
Ekman, Carl D. Reissue, 10131. June 6, 1882. 

Method of treating wood. 
Ekman, Carl D. 260749. July 11, 1882. 

Treating fibrous vegetable substances to obtain fibre suitable for paper- 
making. 
Ekman, Carl D. 307754. Nov. 11, 1884. 

Extraction of gelatine, fat, and similar substances. Patent covers the 
use of sulphite solution, as above. 
Ekman, Carl D., with George Fry and W. B. Espaut. 286817. Oct. 9, 1883. 

Extraction of saccharine matter from vegetable substances. Boils the 
cane, sugar beet, etc., with sulphite solution. 
Ekman, Carl D. 282971. Aug. 14, 1883. 

Obtaining coloring-matters. 
Erwin, Franklin B. 353056. Nov 23, 1886. 

Apparatus. (Digester.) 
Fisher, Robert A. 145496. Dec. 16, 1873. 

Preventing corrosion of iron and steel. 
Flodqvist, Carl W. 348457. Aug. 31, 18S6. 

Digester. 



APPENDIX. 473 

Ford, H. B. 363457. May 24, 18S7. 

Apparatus and process for manufacture of sulphurous acid. 
Frambach, Henry A., and Andrew J. Volbrath. 348159. Aug. 24, 1886. 

Enamel lined digester. 
Frank, Adolph. 376189 and 376190. Jan. 10, 1888. 

Production of sulphite solutions. 
Francke, David Otto. 295865. March 25, 1884. 

Manufacture of paper pulp. 
Francke, David Otto. 304092. Aug. 26, 1884. 

Digester. 
Gamotis, L., and S. Martin. 17S30. July 21, 1857. 

Apparatus for making acid sulphite of lime. 
Getchell, C. E. 378673. Feb. 28, 1888. 

Apparatus for making sulphurous acid. 
Godfrey, C, and Reuben Lighthall. 109508. Nov. 22, 1870. 

Protecting iron against corrosion by applying to iron an electropositive 
metal or alloy. Same idea has recently been proposed for protecting 
sulphite digesters. 
Graham, James Anthony. 280466. July 3, 1883. 

Covering iron with lead. 
Graham, James Anthony. 280171. June 26, 18S3. 

Treating fibrous substances. 
Hanish, E., and M. Schroeder. 376883. Jan. 24, 1888. 

Obtaining sulphurous acid. 
Haskell, J. R. 63044. March 19, 1867. 

Treating and separating vegetable fibres. Not on sulphite process, but 
claim covers first steaming the fibres and then condensing steam by 
shower of cold liquor so as to force liquor into the wood, as in later 
patents of Mitscherlich. 
Hatschek, Moritz. 101011. March 22, 1870. 

Tower apparatus for producing sulphurous acid. 
Hess, J. 434272. August 12, 1890. 

Digester. 
Horsford, E. Iff. 39922. Sept. 15, 1863. 

Preparation of dry sulphite of lime. 
Howell, W. H. 487887. Dec. 13, 1892. 

Liquor apparatus. 
Hughes, H. A. 290642. Dec. 18, 1883. 

Apparatus for preparing sulphuretted cream of lime (sulphite of liraej. 
Jones, N. M. See Curtis, Chas. 
Jones, W. D. 188801. March 27, 1877. 197474. Nov. 27, 1877. 

Apparatus for manufacture of hyclrated sulphurous acid. 
Kellner, Carl or Charles. See also, Ritter, Eugen Baron. 
Kellner, Charles. 352759. Nov. 16, 1886. 

Method of sizing paper, to prevent sulphite and ground wood from turn- 
ing yellow. He precipitates the rosin size with a sulphite salt. 
Keys, William W., and N. W. Williams. 212077. Feb. 4, 1S79. 

Deoxidized bronze. 



474 THE CHEMISTRY OF PAPER-MAKING. 

Keys, William W. 420275. Jan. 28, 1890. 

Sectional bronze digester. 
Ladd, William F. 115327. May 30, 1871. 

Rotary digester without regard to process. 
Lavery, E. 431267. July 1, 1890. 

Digester. 
Little, Arthur D. 351330. Oct. 19, 1886. 

Enamel lining for digesters. 
Lovejoy, F. C. 429692. June 10, 1890. 

Digester. 
Lunge, George. 344322. June 22, 1886. 

Apparatus for treating liquids with gas. 
Marr, William. 705S8. Nov. 5, 1867. 

Manufacture of bisulphite of lime. 
Marshall, George E. See Wheelwright, Charles S. 
Marshall, James F. 312875. Feb. 24, 1885. 

Digester. 
Makin, John. 335943. Feb. 9, 1886. 

Digester. 
Makin, John. 344120. June 22, 1886. 

Leaddined digester. 
Makin, John. 312485. Feb 17, 1S85. 

Combined lead and iron plate. 
Marcelin, Paul. 123713. Feb. 13, 1872. 

Manufacture of sulphurous acid. 
Martin, S. See Gamotis, L. 
Maste, H. A. A. 480334. Aug. 9, 1892. 

Preparation of cellulose from wood. 
Maynard, W. 309968. Dec. 30, 1884. 

Apparatus for charging liquids with gas. 
Maynard, W. 180901. Aug. 8, 1876. 183185. Oct. 10, 1876. 

Apparatus for manufacture of hydrated sulphurous acid. 
McDougall, Isaac S. 298602. May 13, 1884. 

Digester. 
McDougall, Isaac S. 311595. Feb. 3, 1885. 

Manufacture of sulphurous acid. 
Minthorn, Daniel. 307972, Nov. 11, 1884. 319295. June 2, 1885. 

Treating vegetable fibre. 
Mitscherlich, Alex. 395914. Jan. 8, 1889. 

Manufacturing thread from short fibre. 
Mitscherlich, Alex. 263797. Sept. 5, 1882. 

Manufacturing of tannic acid from waste sulphite liquors. 
Mitscherlich, Alex. 28431.9. Sept. 4, 1883. 

Process and digester. 
Mitscherlich, Alex. 377694. March 9, 1886. 

Boiling fibres with sulphites. (Preparation of liquor, process of treating 
wood.) 



APPENDIX. 475 



Mitscherlich, Alex. 336013. Feb. 9, 1886. 

Sizing paper (by material in waste liquor from sulphite boiling). 
Mitscherlich, Alex. 344323. June 22, 1886. 

Paper pulp. (Process and apparatus for manufacturing.) 
Montgomery, T. W., and J. Warlike. 433534. Aug. 5, 1890. 

Apparatus for washing the fumes of sulphur (sulphurous acid). 
Noble, G. R. 345168. July 6, 1886. 

Making lead-lined digesters. 
Noble, G. R. 427892. May 13, 1890. 

Lining boilers with lead. 
Norton, J. 480934. Aug. 16, 1892. 

Lining for tanks. 
Norton, J. 496275. April 25, 1S93. 

Digester. 
Phillips, George R. 307587. Nov. 4, 1884. 

Lining for digesters. 
Pictet, R. P. 404431. June 4, 1889. 

Process of disintegrating fibrous materials. 
Pictet, R. P. 191778. June 12, 1877. 

Apparatus for manufacture of sulphurous anhydride. 
Pictet, R. P. 331323. Dec. 1, 1885. 

Manufacture of pulp from woody matter. 
Pond, Goldsburg H. 354931. Dec. 28, 1886. 

Manufacture of paper pulp from wood. 
Pond, Goldsburg H. 351067. Oct. 19, 1886. 

Machine for manufacture of wood pulp. Manufacture of bronze, and 
its use in digesters, etc., to resist chemicals, sulphuric acid, etc., in 
preparation of wood pulp. 
Pond, Goldsberg H. 351068. Oct. 19, 1886. 

Manufacture of wood pulp. 
Radam, W. 412664. Oct. 8, 1889. 

Apparatus for impregnating liquids with gases. 
Randon, Francois. 337197. March 2, 1S86. 

Apparatus for production of pure sulphurous acid. 
Radford, B. F. 483942. Oct. 4, 1892. 

Digester. 
Reynolds, Eli A. 423531. March 18, 1890. 

Digester. 
Reynoso, A. F. C. 185964. Jan. 2, 1877. 

Apparatus for manufacture of sulphurous acid. 
Ritter, Eugen Baron, and Carl Kellner. 328812. Oct. 20, 1885. 

Apparatus for manufacture of cellulose from wood. 
Ritter, Eugen Baron, and Carl Kellner. 329214. Oct 27, 1885. 

Apparatus (arrangement of ta,nks and digesters). 
Ritter, Eugen Baron, and Carl Kellner. 329215. Oct. 27, 1885. 

Process of manufacturing cellulose. 
Ritter, Eugen Baron, and Carl Kellner. 329216. Oct. 27, 1885. 

Making solutions of bisulphites. 



476 THE CHEMISTRY OF PAPER-MAKING. 

Ritter, Eugen Baron, and Carl Kellner. 329217. Oct. 27, 1885. 

Digester. 
Ritter, Eugen Baron, and Carl Kellner. 338557. March 23, 1886. 

Apparatus for manufacture of sulphurous acid. 
Ritter, Eugen Baron, and Carl Kellner. 338558. March 23, 1886. 

Process for manufacturing sulphites. 
Russell, G. F. 445235. Jan. 27, 1891. 

Digester. 
Russell, G. F. Reissue, 11282. Nov. 15, 1892. 

Digester. 
Russell, George W. 341434 and 341435. May 4, 1886. 

Digester. 
Saunders, John. 234431. Nov. 16, 1880. 

Slide valve gate for digesters. 
Schenck, Garrett. 363173. May 17, 1887. 

Process of, and apparatus for, charging liquids with gas. 
Schenck, Garrett. 395082. Dec. 25, 1888. 

Apparatus for preparing solutions of bisulphites. 
Schnurmann, Heinrich, and Gotthold Closs. 360484. April 5, 1887. 

Apparatus. (Digester, heater, and circulation apparatus.) 
Schroeder, M. See Hanish, E. 
Smith, Sidney. 428149. May 20, 1890. 

Lead lined digester. 
Smith, Sidney. 421201. Feb. 11, 1890. ' 

Sulphur burner. 
Smith, S. 428149. May 20, 1890. 

Digester. 
Smith, S. 443922. Dec. 30, 1890. 

Digester. 
Smith, S. 443923. Dec. 30, 1890. 

Digester. 
Smith, S. 443924. Dec. 30, 1890. 

Digester. 
Spence, Peter. 248541. Oct. 18, 1881. 

Furnace for burning pyrites. 
Spiro., J. See Wendler, A. 
Springer, C. C. 411838. Oct. 1, 1889. 

Digester. 
Springer, C. C. 335046. Jan. 26, 1886. 

Digester. 
Stebbins, Henry W. 405279. June 18, 1889. 

Digester. 
Tilghman, B. C. 70485. Nov. 5, 1867. 

Treating vegetable substances for making paper pulp. The foundation 
patent. 
Tilghman, B. C. 92229. July 6, 1869. 

Process of treating vegetable substances to obtain fibre. 



APPENDIX. 477 

Tompkins, John D. 401609. April 16, 1889. 

Digester. 
Turner, Walter J. 123799. Feb. 20, 1872. 

Apparatus for manufacture of bisulphites. 
Wagg, S. R. 373703. Nov. 22, 1887. 

Digester. 
Wagg, S. R. 390727. Oct. 9, 1888. 

Lining for digesters. 
Wagg, S. R." 440242. Nov. 11, 1890. 

Digester. 
Wagg, S. R. 446041. Feb. 10, 1891. 

Digester. 
Walker, G. R. 310753. Jan. 13, 18S5. 

Treating yucca to obtain fibre. Uses borax liquor and sulphurous acid. 
Warnke, J. See Montgomery, T. W. 
Wendler, A., and J. Spiro. 446652. 

Liquor apparatus. 
Wheelwright, Charles S. 337720. 337721. March 9, 1886. 

Digester or converter. 
Wheelwright, Charles S. 307608. Nov. 4,1884. 

Digester. 
Wheelwright, Charles S., and George E. Marshall. 307609. Nov. 4, 1884. 

Apparatus for treating wood. 
Williams, N. W. See Keys, William W. 
Wurtz, Henry. 252287. Jan. 10, 1882. 

Treating pyrites for manufacture of sulphurous acid. 
Zier, Michael. See Bremaker, Charles. 



478 



THE CHEMISTRY OF PAPER-31AKING. 



METRIC WEIGHTS AND MEASURES. 

For the complicated system of weights and measures in use in this 
country and in England, most chemists substitute the very simple 
metric system. The unit of the system is the metre, a rod of plati- 
num deposited in the Archives of France, which, when constructed 
was supposed to be one ten-millionth part of the quadrant of a great 
circle encompassing the earth on the meridian of Paris. 

Measures of Length. — The metre measures 39.37 inches. It is 
multiplied and subdivided by 10 for the higher and lower measures 
of length. 





Metres. 


Inches. 


kilometre 


1000.0 


39370.0 


hectometre 


100.0 


■ 3937.0 


decametre 


10.0 


393.70 


metre 


1.0 


39.37 


decimetre 


0.1 


3.937 


centimetre 


0.01 


0.3937 


millimetre 


0.001 


0.03937 



The Greek prefixes deca, hecto, and kilo are used to represent the 
numbers 10, 100, and 1000, respectively, and the Latin deci, centi, and 
milli signify a tenth, hundredth, and thousandth. The prefixes are 
used with the same meaning in the other measures. The decimetre 
is very nearly 4 inches in length. This affords an easy method of 
roughly translating measures of the one denomination into those of 
the other. 

Measures of Capacity. — The measure of capacity is derived from 
that of length by taking one cubic decimetre as the unit. This is 
named the litre, the capacity of which and that of its derivatives in the 
United States measures are appended : — 





Litres. 


Cubic inches. 


Pints (U. S.). 


kilolitre 


1000.0 


61027.0 


2113.1 


hectolitre 


100.0 


6102.7 


211.31 


decalitre 


10.0 


610.27 


21.131 


litre 


1.0 


61.027 


2.1131 


decilitre 


0.1 


6.1027 


0.2113 


centilitre 


0.01 


0.61027 


0.02113 


millilitre 


0.001 


0.061027 


0.002113 



APPENDIX. 



479 



The litre being the capacity of a cubic decimetre, it is evident that 
the millilitre equals in volume a cubic centimetre, and this latter 
term, or its abbreviation (c.c), is very frequently used in preference 
to millilitre ; thus a pipette is said to contain 50 c.c, and a litre flask 
is often called a 1000 c.c. flask. 

A cubic inch is equal to 16.3 cubic centimetres. 

Measures of Weight. — The weight of one cubic centimetre of 
distilled water at its maximum density (4° C.) is taken as the unit 
of weight, and is called a gramme or gram. The subdivision and 
multiples are again the same. 





Grammes. 


Grains. 


Avoirdupois ounces. 


kilogramme 


1000.0 


15432.3 


35.2739 


hectogramme 


100.0 


1543.23 


3.52739 


decagramme 


10.0 


154.323 


0.352739 


gramme 


1.0 


15.4323 


0.0352739 

1 


decigramme 


0.1 


1.5432 


0.003527 


centigramme 


0.01 


0.15432 


0.0003527 


milligramme 


0.001 


0.015432 


0.00003527 



A kilogramme is a little over 2 lbs. 3| oz., and a hectogramme d\ oz. 
An ounce avoirdupois equals 28.35 grammes. 

The relation between the weight and volume of water is seen to be 
a very simple one, the volume being the same number of cubic centi- 
metres as the weight in grammes. With other liquids the volume in 
cubic centimetres x specific gravity = weight in grammes. 



RELATIONS BETWEEN THERMOMETERS. 

In Fahrenheit's thermometer, the freezing-point of water is placed 
at 32°, and the boiling-point at 212°, and the number of intervening 
degrees is 180. 

The Centigrade, or Celsius's thermometer, which is now recognized 
in the United States Pharmacopoeia, and has been adopted gener- 
ally by scientists, marks the freezing-point 0, and the boiling-point 
100. 

From the above statement it is evident that 180° of Fahrenheit are 
equal to 100° of Centigrade ; or, 1° of the first is equal to -f of a degree 
of the second. It is easy, therefore, to convert the degrees of one to 



480 



THE CHEMISTRY OF PAPER-MAKING. 



the equivalent number of degrees of the other; but in ascertaining the 
corresponding point of the different scales it is necessary to take into 
consideration their different modes of graduation. Thus, as the of 
Fahrenheit is at 32° below the point at which that of the Centi- 
grade is placed, this number must be taken into account in the calcula- 
tion. 

If any degree on the Centigrade scale, either above or below 0, be 
multiplied by 1.8, the result will in either case be the number of 
degrees above or below 32, or the freezing-point, Fahrenheit. 

The number of degrees between any point on the Fahrenheit scale 
and 32, if divided by 1.8, will give the corresponding point on the 
Centigrade. 

Thermometry Equivalents, 

According to the Centigrade and Fahrenheit Scales. 





c. 


F. 


C. 


F. 


C. 


F. 


-40 


-40.0 


3 


37.4 


30 


86.0 


-35 


-31.0 


4 


39.2 


31 


87.8 


-30 


-22.0 


5 


41.0 


32 


89.6 


-25 


-13.0 


6 


42.8 


33 


91.4 


-20 


- 4.0 


7 


44.6 


34 


93.2 


-19 


- 2.2 


8 


46.4 


35 


95.0 


-18 


- 0.4 


9 


48.2 


36 


96.8 


-17 


+ 1-4 


10 


50.0 


37 


98.6 


-16 


3.2 


11 


51.8 


38 


100.4 


-15 


5.0 


12 


53.6 


39 


100.2 


-14 


6.8 


13 


55.4 


40 


104.0 


-13 


8.6 


14 


57.2 


41 


105.8 


-12 


10.4 


15 


59.0 


42 


107.6 


-11 


12.2 


16 


60.8 


43 


109.4 


-10 


14.0 


17 


62.6 


44 


111.2 


- 9 


15.8 


18 


64.4 


45 


113.0 


- 8 


17.6 


19 


66.2 


46 


114.8 


- 7 


19.4 


20 


68.0 


47 


116.6 


- 6 


21.2 


21 


69.8 


48 


118.4 


- 5 


23.0 


22 


71.6 


49 


120.2 


- 4 


24.8 


23 


73.4 


50 


122.0 


- 3 


26.6 


24 


75.2 


51 


123.8 


v_ 2 


28.4 


25 


77.0 


52 


125.6 


- 1 


30.2 


26 


78.8 


53 


127.4 





32.0 


27 


80.6 


54 


129.2 


+ 1 


33.8 


28 


82.4 


55 


131.0 


2 


35.6 


29 


84.2 


56 


132.8 



APPENDIX. 



481 



Thermometry Equivalents {continued). 



c. 


F. 


C. 


F. 


C. 


F. 


57 


134.6 


92 


197.6 


127 


260.6 


58 


136.4 


93 


199.4 


128 


262.4 


59 


138.2 


94 


201.2 


129 


264.2 


60 


140.0 


95 


203.0 


130 


266.0 


61 


141.8 


96 


204.8 


131 


267.8 


62 


143.6 


97 


206.6 


132 


269.6 


63 


145.4 


98 


208.4 


133 


271.4 


64 


147.2 


99 


210.2 


134 


273.2 


65 


149.0 


100 


212.0 


135 


275.0 


66 


150.8 


101 


213.8 


136 


276.8 


67 


152.6 


102 


215.6 


137 


278.6 


68 


154.4 


103 


217.4 


138 


280.4 


69 


156.2 


104 


219.2 


139 


282.2 


70 


158.0 


105 


221.0 


140 


284.0 


71 


159.8 


106 


222.8 


141 


285.8 


72 


161.6 


107 


224.6 


142 


287.6 


73 


163.4 


108 


226.4 


143 


289.4 


74 


165.2 


109 


228.2 


144 


291.2 


75 


167.0 


110 


230.0 


145 


293.0 


76 


168.8 


111 


231.8 


146 


294.8 


77 


170.6 


112 


233.6 


147 


296.6 


78 


172.4 


113 


235.4 


148 


298.4 


79 


174.2 


114 


237.2 


149 


300.2 


80 


176.0 


115 


239.0 


150 


302.0 


81 


177.8 


116 


240.8 


151 


303.8 


82 


179.6 


117 


242.6 


152 


305.6 


83 


181.4 


118 


244.4 


153 


307.4 


84 


183.2 


119 


246.2 


154 


309.2 


85 


185.0 


120 


248.0 


155 


311.0 


86 


186.8 


121 


249.8 


156 


312.8 


87 


188.6 


122 


251.6 


157 


314.6 


88 


190.4 


123 


253.4 


158 


316.4 


89 


192.2 


124 


255.2 


159 


318.2 


90 


194.0 


125 


257.0 


160 


320.0 


91 


195.8 


126 


258.8 









482 



THE CHEMISTRY OF PAPER-MAKING. 



Specific Gravity corresponding to Degrees of Baume's Hydrometer for 
Liquids Lighter than Water. 



Degree of 
hydrometer. 


Specific gravity. 


Degree of 
hydrometer. 


Specific gravity. 


Degree of 
hydrometer. 


Specific gravity. 


10 


1.000 


33 


0.862 


56 


0.758 


11 


0.993 


34 


0.857 


57 


0.754 


12 


0.986 


35 


0.852 


58 


0.750 


13 


0.979 


36 


0.847 


59 


0.746 


14 


0.973 


37 


0.842 


60 


0.742 


15 


0.966 


38 


0.837 


61 


0.738 


16 


0.960 


39 


0.832 


62 


0.735 


17 


0.953 


40 


0.827 


63 


0.731 


18 


0.947 


41 


0.823 


64 


0.727 


19 


0.941 


42 


0.818 


65 


0.724 


20 


0.935 


43 


0.813 


66 


0.720 


21 


0.929 


44 


0.809 


67 


0.716 


22 


0.923 


45 


0.804 


68 


0.713 


23 


0.917 


46 


0.800 


69 


0.709 


24 


0.911 


47 


0.795 


70 


0.706 


25 


0.905 


48 


0.791 


71 


0.702 


26 


0.900 


49 


0.787 


72 


0.699 


27 


0.894 


50 


0.783 


73 


0.696 


28 


0.889 


51 


0.778 


74 


0.692 


29 


0.883 


52 


0.774 


75 


0.689 


30 


0.878 


53 


0.770 


76 


0.686 


31 


0.872 


54 


0.766 


77 


0.682 


32 


0.867 


55 


0.762 







Percentage of Sodium Chloride in Solutions of Different Specific 

Gravities. 



Specific gravity. 


Per cent. 
NaCl. 


Specific gravity. 


Per cent. 

NaCl. 


Specific gravity. 


Per cent. 

NaCl. 


1.00725 


1 


1.07335 


10 


1.14315 


19 


1.01450 


2 


1.08097 


11 


1.15107 


20 


1.02174 


3 


1.08859 


12 


1.15931 


21 


1.028999 


4 


1.09622 


13 


1.16755 


22 


1.03624 


5 


1.10384 


14 


1.17580 


23 


1.04366 


6 


1.11146 


15 


1.18404 


24 


1.05108 


7 


1.11938 


16 


1.19228 


25 


1.05851 


8 


1.12730 


17 


1.20098 


26 


1.06593 


9 


1.13523 


18 


1.20433 


26.395 



APPENDIX. 



483 



Specific Gravity corresponding to Degrees of Baume's Hydrometer for 
Liquids Heavier than Water. 



Degree of 
hydrometer. 


Specific gravity. 


Degree of 
hydrometer. 


Specific gravity. 


Degree of 
hydrometer. 


Specific gravity. 





1.000 


26 


1.221 


52 


1.566 


1 


1.007 


27 


1.231 


53 


1.583 


2 


1.014 


28 


1.242 


54 


1,601 


3 


1.022 


29 


1.252 


55 


1.618 


4 


1.029 


30 


1.261 


56 


1.637 


5 


1.036 


31 


1.275 


57 


1.656 


6 


1.044 


32 


1.286 


58 


1.676 


7 


1.052 


33 


1.298 


59 


1.695 


8 


1.060 


34 


1.309 


60 


1.715 


9 


1.067 


35- 


1,321 


61 


1.736 


10 


1.075 


36 


1.334 


62 


1.758 


11 


1.083 


37 


1.346 


63 


1.779 


12 


1.091 


38 


1.359 


64 


1.801 


13 


1.100 


39 


1.372 


65 


1.823 


14 


1.108 


40 


1.384 


66 


1.847 


15 


1.116 


41 


1.398 


67 


1.872 


16 


1.125 


42 


1.412 


68 


1.897 


17 


1.134 


43 


1.426 


69 


1.921 


18 


1.143 


44 


1.440 


70 


1.946 


19 


1.152 


45 


1.454 


71 


1.974 


20 


1.161 


46 


1.470 


72 


2.002 


21 


1.171 


47 


1.485 


73 


2.031 


22 


1.180 


48 


1.501 


74 


2.059 


23 


1.190 


49 


1.516 


75 


2.087 


24 


1.199 


50 


1.532 






25 


1.210 


51 


1.549 







Percentage of Oxalic Acid in Solutions of Different Specific Gravity 

at 15° C. 



Specific gravity. 


Per cent. 
C,H,0 4 
+ 2 H 2 0. 


Specific gravity. 


Per cent. 
C,H,0 4 
+ 2 H 2 0. 


Specific gravity. 


Per cent. 
C 2 H„0 4 
+ 2 11,0. 


1.0032 


1 


1.0182 


6 


1.0271 


10 


1.0064 


2 


1.0204 


7 


1.0289 


11 


1.0096 


3 


1.0226 


8 


1.0309 


12 


1.0128 


4 


1.0248 


9 


1.0320 


12.6 


1.0160 


5 











484 



THE CHEMISTRY OF PAPER-MAKING. 



Specific Gravity corresponding to Degrees of Twaddle's Hydrometer. 



Degrees 
Twaddle. 


Specific 
gravity. 


Degrees 
Twaddle. 


Specific 
gravity. 


Degrees 
Twaddle. 


Specific 
gravity. 





1.000 


43 


1.215 


86 


1.430 


1 


1.005 


44 


1.220 


87 


1.435 


2 


1.010 


45 


1.225 


88 


1.440 


3 


1.015 


46 


1.230 


89 


1.445 


4 


1.020 


47 


1.235 


90 


1.450 


5 


1.025 


48 


1.240 


91 


1.455 


6 


1.030 


49 


1.245 


92 


1.460 


7 


1.035 


50 


1.250 


93 


1.465 


8 


1.040 


51 


1.255 


94 


1.470 


9 


1.045 


52 


1.260 


95 


1.475 


10 


1.050 


53 


1.265 


96 


1.480 


11 


1.055 


54 


1.270 


97 


1.485 


12 


1.060 


55 


1.275 


98 


1.490 


13 


1.Q65 


56 


1.280 


99 


1.495 


14 


1.070 


57 


1.285 


100 


1.500 


15 


1.075 


58 


1.290 


101 


1.505 


16 


1.080 


59 


1.295 


102 


1.510 


17 


1.085 


60 


1.300 


103 


1.515 


18 


1.090 


61 


1.305 


104 


1.520 


19 


1.095 


62 


1.310 


105 


1.525 


20 


1.100 


63 


1.315 


106 


1.530 


21 


1.105 


64 


1.320 


107 


1.535 


22 


1.110 


65 


1.325 


108 


1.540 


23 


1.115 


66 


1.330 


109 


1.545 


24 


1.120 


67 


1.335 


110 


1.550 


25 


1.125 


68 


1.340 


111 


1.555 


26 


1.130 


69 


1.345 


112 


1.560 


27 


1.135 


70 


1.350 


113 


1.565 


28 


1.140 


71 


1.355 


114 


1.570 


29 


1.145 


72 


1.360 


115 


1.575 


30 


1.150 


73 


1.365 


116 


1.580 


31 


1.155 


74 


1.370 


117 


1.585 


32 


1.160 


75 


1.375 


118 


1.590 


33 


1.165 


76 


1.380 


119 


1.595 


34 


1.170 


77 


1.385 


120 


1.600 


35 


1.175 


78 


1.390 


121 


1.605 


36 


1.180 


79 


1.395 


122 


1.610 


37 


1.185 


80 


1.400 


123 


1.615 


38 


1.190 


81 


1.405 


124 


1.620 


39 


1.195 


82 


1.410 


125 


1.625 


40 


1.200 


83 


1.415 


126 


1.630 


41 


1.205 


84 


1.420 


127 


1.635 


42 


1.210 


85 


1.425 


128 


1.640 



APPENDIX. 



485 



Specific Gravity corresponding to Degrees of Twaddle's Hydrometer 

(continued). 



Degrees 
Twaddle. 


Specific 
gravity. 


Degrees 
Twaddle. 


Specific 
gravity. 


Degrees 
Twaddle. 


Specific 
gravity. 


129 


1.645 


153 


1.765 


177 


1.885 


130 


1.650 


154 


1.770 


178 


1.890 


131 


1.655 


155 


1.775 


179 


1.895 


132 


1.660 


156 


1.780 


180 


1.900 


133 


1.665 


157 


1.785 


181 


1.905 


134 


1.670 


158 


1.790 


182 


* 1.910 


135 


1.675 


159 


1.795 


183 


1.915 


136 


1.680 


160 


1.800 


184 


1.920 


137 


1.685 


161 


1.805 


185 


1.925 


138 


1.690 


162 


1.810 


186 


1.930 


139 


1.695 


163 


1.815 


187 


1.935 


140 


1.700 


164 


1.820 


188 


1.940 


141 


1.705 


165 


1.825 


189 


1.945 


142 


1.710 


166 


1.830 


190 


1.950 


143 


1.715 


167 


1.835 


191 


1.955 


144 


1.720 


168 


1.840 


192 


1.960 


145 


1.725 


169 


1.845 


193 


1.965 


146 


1.730 


170 


1.850 


194 


1.970 


147 


1.735 


171 


1.855 


195 


1.975 


148 


1.740 


172 


1.860 


196 


1.980 


149 


1.745 


173 


1.865 


197 


1.985 


150 


1.750 


174 


1.870 


198 


1.990 


151 


1.755 


175 


1.875 


199 


1.995 


152 


1.760 


176 


1.880 


200 


2.000 



486 



THE CHEMISTRY OF PAPER-MAKING. 



Table of the Elements, together with their Symbols and Approximate 

Atomic Weights. 1 





Symbols. 


Atomic weight. 




Symbols. 


Atomic weight. 


Aluminum . . 


Al 


27.5 


Molybdenum . 


Mo 


96 


Antimony 






Sb 


122 


Nickel . . . 


Ni 


59 


Arsenic . 






As 


75 


Niobium . . 


Nb 


94 


Barium . 






Ba 


137 


Nitrogen . . 


N 


14 


Beryllium 






Be 


9.4 


Osmium 


Os 


199 


Bismuth . 






Bi 


208 


Oxygen . . 


O 


16 


Boron 






B 


11 


Palladium . 


Pd 


106 


Bromine . 






Br 


80 


Phosphorus . 


P 


31 


Cadmium 






Cd 


112 


Platinum . . 


Pt 


197.18 


Csesium . 






Cs 


133 


Potassium . 


K 


39 


Calcium . 






Ca 


40 


Rhodium . . 


Rh 


104 


Carbon . 






C 


12 


Rubidium . 


Rb 


85 


Cerium . 






Ce 


137 


Selenium . . 


Se 


79 


Chlorine . 






CI 


35.5 


Ruthenium 


Ru 


104 


Chromium 






Cr 


52.5 


Silicon . . 


Si 


28 


Cobalt . 






Co 


59 


Silver . . . 


Ag 


108 


Copper . 






Cu 


63.5 


Sodium . . 


Na ' 


23 


Didymium 






Di 


144 


Strontium . 


Sr 


87.5 


Erbium . 






Er 


170.6 


Sulphur . . 


S 


32 


Fluorine . 






E 


19 


Tantalium . 


Ta 


182 


Gold . . 






Au 


197 


Tellurium . 


Te 


125 


Hydrogen 






H 


1 


Thallium . . 


Tl 


204 


Indium . 






In 


113 


Thorium . 


Th 


231.5 


Iodine 






I 


127 


Tin .... 


Sn 


118 


Iridium . 






Ir 


193 


Titanium . . 


Ti 


48 


Iron . . 






Fe 


56 


Uranium . 


Ur 


240 


Lanthanum 






La 


139 


Vanadium . . 


V 


51 


Lead . . 






Pb 


207 


Wolframium . 


w 


184 


Lithium . 






Li 


7 


Yttrium 


Y 


88 


Magnesium 






Mg 


24 


Zinc .... 


Zn 


65 


Manganese 






Mn 


55 


Zirconium . 


Zr 


90 


Mercury . 






Hg 


200 









1 The atomic weights here given are those used by Lunge in his "Alkali-Maker's Handbook." 



APPENDIX. 



487 



Temperature of Saturated Steam at Different Pressures. 



Pressure per 
square inch. 


Temperature. 
Degrees F. 


Pressure per 
square inch. 


Temperature. 
Degrees F. 


Pressure per 
square inch. 


Temperature. 
Degrees F. 


1 


102.1 


34 


257.6 


68 


300.9 


2 


126.3 


35 


259.3 


69 


301.9 


3 


141.6 


36 


260.9 


70 


302.9 


4 


153.1 


37 


262.6 


71 


303.9 


5 


162.3 


38 


264.2 


72 


304.8 


6 


170.2 


39 


265.8 


73 


305.7 


7 


176.9 


40 


267.3 


74 


306.6 


8 


182.9 


41 


268.7 


75 


307.5 


9 


188.3 


42 


270.2 


76 


308.4 


10 


193.3 


43 


271.6 


77 


309.3 


11 


197.8 


44 


273.0 


78 


310.2 


12 


202.0 


45 


274.4 


79 


311.1 


13 


205.9 


46 


275.8 


80 


312.0 


14 


209.6 


47 


277.1 


81 


312.8 


14.7 


212.0 


48 


278.4 


82 


313.6 


15 


213.1 


49 


279.7 


83 


314.5 


16 


216.3 


50 


281.0 


84 


315.3 


17 


219.6 


51 


282.3 


85 


316.1 


18 


222.4 


52 


283.5 


86 


316.9 


19 


225.3 


53 


284.7 


87 


317.8 


20 


228.0 


54 


285.9 


88 


318.6 


21 


230.6 


55 


287.1 


89 


319.4 


22 


233.1 


56 


288.2 


90 


320.2 


23 


235.5 


57 


289.3 


91 


321.0 


24 


237.8 


58 


290.4 


92 


321.7 


25 


240.1 


59 


291.6 


93 


322.5 


26 


242.3 


60 


292.7 


94 


323.3 


27 


244.4 


61 


293.8 


95 


324.1 


28 


246.4 


62 


294.8 


96 


324.8 


29 


248.4 


63 


295.9 


97 


325.6 


30 


250.4 


64 


296.9 


98 


326.3 


31 


252.2 


65 


298.0 


99 


327.1 


32 


254.1 


66 


299.0 


100 


327.9 


33 


255.9 


67 


300.0 







488 



THE CHEMISTRY OF PAPER-MAKING. 



Percentage of Sulphuric Acid for Different Specific Gravities. 



Specific gravity at 15° C. 


Per cent, by weight 

c. p. sulphuric acid, 

H 2 S0 4 . 


Specific gravity at 15° C. 


Per cent, by weight 

c.p. sulphuric acid, 

H 2 S0 4 . 


1.00 


0.09 


1.42 


52.13 


1.01 


1.57 


1.43 


53.11 


1.02 


3.03 


1.44 


54.07 


1.03 


4.49 


1.45 


55.03 


1.04 


5.96 


1.46 


55.97 


1.05 


7.37 


1.47 


56.90 


1.06 


8.77 


1.48 


57.83 


1.07 


10.19 


1.49 


58.74 


1.08 


11.60 


1.50 


59.70 


1.09 


12.99 


1.51 


60.65 


1.10 


14.35 


1.52 


61.59 


1.11 


15.71 


1.53 


62.53 


1.12 


17.01 


1.54 


63.43 


1.13 


18.31 


1.55 


64.26 


1.14 


19.61 


1.56 


65.08 


1.15 


20.91 


1.57 


65.90 


1.16 


22.19 


1.58 


66.71 


1.17 


23.47 


1.59 


67.59 


1.18 


24.76 


1.60 


68.51 


1.19 


26.04 


1.61 


69.43 


1.20 


27.32 


1.62 


70.32 


1.21 


28.58 


1.63 


71.16 


1.22 


29.84 


1.64 


71.99 


1.23 


31.11 


1.65 


72.82 


1.24 


32.28 


1.66 


73.64 


1.25 


33.43 


1.67 


74.51 


1.26 


34.57 


1.68 


75.42 


1.27 


35.71 


1.69 


76,30 


1.28 


36.87 


1.70 


77.17 


1.29 


38.03 


1.71 


78.04 


1.30 


39.19 


1.72 


78.92 


1.31 


40.35 


1.73 


79.80 


1.32 


41.50 


1.74 


80.68 


1.33 


42.66 


1.75 


81.56 


1.34 


43.74 


1.76 


82.44 


1.35 


44.82 


1.77 


83.32 


1.36 


45.88 


1.78 


84.50 


1.37 


46.94 


1.79 


85.70 


1.38 


48.00 


1.80 


86.90 


1.39 


49.06 


1.81 


88.30 


1.40 


50.11 


1.82 


90.05 


1.41 


51.15 


1.822 


90.40 



APPENDIX. 



489 



Percentage of Sulphuric Acid for Different Specific Gravities 

(continued) . 



Specific gravity at 15° C. 


Per cent, by weight 

c.p. sulphuric acid, 

H 2 S0 4 . 


Specific gravity at 15° C. 


Per cent, by weight 

c.p. sulphuric acid, 

H 2 S0 4 . 


1.824 


90.80 


1.840 


95.60 


1.826 


91.25 


1.8110 


97.00 


1.828 


91.70 


1.8415 


97.70 


1.830 


92.10 


1.8410 


98.20 


1.832 


92.52 


1.8400 


99.20 


1.834 


93.05 


1.8390 


99.70 


1.836 


93.80 


1.8385 


99.95 


1.838 


94.60 







Table showing how to prepare Sulphuric Acid of Any Strength by 
mixing Different Proportions of Acid and Water. 

Column a shows how many parts of oil of vitriol of 1.840 specific gravity (66° B, 168° Twaddle's) 
must be mixed with 100 parts water, at 15° or 20 D , in order to obtain an acid of the specific gravity 6. 



a 


b 


a 


b 


a 


b 


1 


1.009 


130 


1.456 


■370 


1.723 


2 


1.015 


140 


1.473 


380 


1.727 


5 


1.035 


150 


1.490 


390 


1.730 


10 


1.060 


160 


1.510 


400 


1.733 


15 


1.090 


170 


1.530 


410 


1.737 


20 


1.113 


180 


1.543 


420 


1.740 


25 


1.140 


190 


1.556 


430 


1.743 


30 


1.165 


200 


1.568 


440 


1.746 


35 


1.187 


210 


1.580 


450 


1.750 


40 


1.210 


220 


1.593 


460 


1.754 


45 


1.229 


230 


1.606 


470 


1.757 


50 


1.248 


240 


1.620 


480 


1.760 


55 


1.265 


250 


1.630 


490 


1.763 


60 


1.280 


260 


1.640 


500 


1.766 


65 


1.297 


270 


1.648 


510 


1.768 


70 


1.312 


280 


1.654 


520 


1.770 


75 


1.326 


290 


1.667 


530 


1.772 


80 


1.340 


300 


1.678 


540 


1.774 


85 


1.357 


310 


1.689 


550 


1.776 


90 


1.372 


320 


1.700 


560 


1.777 


95 


1.386 


330 


1.705 


580 


1.778 


100 


1.398 


340 


1.710 


590 


1.780 


110 


1.420 


350 


1.714 


600 


1.782 


120 


1.438 


360 


1.719 







490 



THE CHEMISTRY OF PAPER-MAKING. 



Percentage of Nitric Acid for Different Specific Gravities. 





Specific gravity. 


Per cent, by weight of 
nitric acid. 


Specific gravity. 


Per cent, by weight of 
nitric acid. 


1.000 


0.10 


1.215 


34.55 


1.005 


1.00 


1.220 


35.28 


1.010 


1.90 


1.225 


36.03 


1.015 


2.80 


1.230 


36.78 


1.020 


3.70 


1.235 


37.53 


1.025 


4.60 


1.240 


38.29 


1.030 


5.50 


1.245 


39.05 


1.035 


6.38 


1.250 


39.82 


1.040 


7.26 


1.255 


40.58 


1.045 


8.13 


1.260 


41.34 


1.050 


8.99 


1.265 


42.10 


1.055 


9.84 


1.270 


42.87 


1.060 


10.68 


1.275 


43.64 


1.065 


11.51 


1.280 


44.41 


1.070 


12.33 


1.285 


45.18 


1.075 


13.15 


1.290 


45.95 


1.080 


13.95 


1.295 


46.72 


1.085 


14.74 


1.300 


47.49 


1.090 


15.53 


1.305 


48.26 


1.095 


16.32 


1.310 


49.07 


1.100 


17.11 


1.315 


49.89 


1.105 


17.89 


1.320 


50.71 


1.110 


18.67 


1.325 


51.53 


1.115 


19.45 


1.330 


52.37 


1.120 


20.23 


1.335 


53.22 


1.125 


21.00 


1.340 


55.07 


1.130 


21.77 


1.345 


54.93 


1.135 


22.54 


1.350 


55.79 


1.140 


23.31 


1.355 


56.66 


1.145 


24.08 


1.360 


57.57 


1.150 


24.84 


1.365 


58.48 


1.155 


25.60 


1.370 


59.39 


1.160 


26.36 


1.375 


60.30 


1.165 


27.12 


1.380 


61.27 


1.170 


27.88 


1.385 


62.24 


1.175 


28.63 


1.390 


63.23 


1.180 


29.38 


1.395 


64.25 


1.185 


30.13 


1.400 


65.30 


1.190 


30.88 


1.405 


66.40 


1.195 


31.62 


1.410 


67.50 


1.200 


32.36 


1.415 


68.63 


1.205 


33.09 


1.420 


.69.80 


1.210 


33.82 


1.425 


70.98 



APPENDIX. 



491 



Percentage of Nitric Acid for Different Specific Gravities (continued). 



Specific gravity. 


Per cent, by weight of 
nitric acid. 


Specific gravity. 


Per cent, by weight of 
nitric acid. 


1.430 


72.17 


1.504 


96.00 


1.435 


73.39 


1.505 


96.39 


1.440 


74.68 


1.506 


96.76 


1.445 


75.98 


1.507 


97.13 


1.450 


77.28 


1.508 


97.50 


1.455 


78.60 


1.509 


97.84 


1.460 


79.98 


1.510 


98.10 


1.465 


81.42 


1.511 


98.32 


1.470 


82.90 


1.512 


98.53 


1.475 


84.45 


1.513 


98.73 


1.480 


86.05 


1.514 


98.90 


1.485 


87.70 


1.515 


99.07 


1.490 


89.60 


1.516 


99.21 


1.495 


91.60 


1.517 


99.34 


1.500 


94.09 


1.518 


99.46 


1.501 


94.60 


1.519 


99.57 


1.502 


95.08 


1,520 


99.67 


1.503 


95.55 







Percentage of Hydrochloric . Acid in Solutions of Different Specific 
Gravities at 15° C. 



Specific gravity. 


Per cent. HC1. 


Specific gravity. 


Per cent. HC1. 


Specific gravity. 


Per cent. HC1. 


1.000 


0.16 


1.070 


14.17 


1.140 


27.66 


1.005 


1.15 


1.075 


15.16 


1.145 


28.61 


1.010 


2.14 


1.080 


16.15 


1.150 


29.57 


1.015 


3.12 


1.085 


17.13 


1.155 


30.55 


1.020 


4.13 


1.090 


18.11 


1.160 


31.52 


1.025 


5.15 


1.095 


19.06 


1.165 


32.49 


1.030 


6.15 


1.100 


20.01 


1.170 


33.46 


1.035 


7.15 


1.105 


20.97 


1.175 


34.42 


1.040 


8.16 


1.110 


21.92 


1.180 


35.39 


1.045 


9.16 


1.115 


22.86 


1.185 


36.31 


1.050 


10.17 


1.120 


23.82 


1.190 


37.23 


1.055 


11.18 


1.125 


24.78 


1.195 


38.16 


1.060 


12.19 


1.130 


25.75 


1.200 


39.11 


1.065 


13.19 


1.135 


26.70 







492 



THE CHEMISTRY OF PAPER-MAKING. 



Percentage of Absolute Acetic Acid in Acetic Acid of Different 
Densities. (Oudemans.) Temperature 15° C. 



Per cent. 


Specific gravity. 


Per cent. 


Specific gravity. 


Per cent. 


Specific gravity. 


100 


1.0553 


66 


1.0717 


33 


1.0447 


99 


1.0580 


65 


1.0712 


32 


1.0436 


98 


1.0604 


64 


1.0707 


31 


1.0424 


97 


1.0625 


63 


1.0702 


30 


1.0412 


96 


1.0644 


62 


1.0697 


29 


1.0400 


95 


1.0660 


61 


1.0691 


28 


1.0388 


94 


1.0674 


60 


1.0685 


27 


1.0375 


93 


1.0686 


59 


1.0679 


26 


1.0363 


92 


1.0696 


58 


1.0673 


25 


1.0350 


91 


1.0705 


57 


1.0666 


24 


1.0337 


90 


1.0713 


56 


1.0660 


23 


1.0324 


89 


1.0720 


55 


1.0653 


22 


1.0311 


88 


1.0726 


54 


1.0646 


21 


1.0298 


87 


1.0731 


53 


1.0638 


20 


1.0284 


86 


1.0736 


52 


1 .0631 


19 


1.0270 


85 


1.0739 


51 


1.0623 


18 


1.0256 


84 


1.0742 


50 


1.0615 


17 


1.0242 


83 


1.0744 


49 


1.0607 


16 


1.0228 


82 


1.0746 


48 


1.0598 


15 


1.0214 


81 


1.0747 


47 


1.0589 


14 


1.0201 


80 


1.0748 


46 


1.0580 


13 


1.0185 


79 


1.0748 


45 


1.0571 


12 


1.0171 


78 


1.0748 


44 


1.0562 


11 


1.0157 


77 


1.0748 


43 


1.0552 


10 


1.0142 


76 


1.0747 


42 


1.0543 


9 


1.0127 


75 


1.0746 


41 


1.0533 


8 


1.0113 


74 


1.0744 


40 


1.0523 


7 


1.0098 


73 


1.0742 


39 


1.0513 


6 


1.0083 


72 


1.0740 


38 


1.0502 


5 


1.0067 


71 


1.0737 


37 


1.0492 


4 


1.0052 


70 


1.0733 


36 


1.0481 


3 


1.0037 


69 


1.0729 


35 


1.0470 


2 


1.0022 


68 


1.0725 


34 


1.0459 


1 


1.0007 


67 


1.0721 











APPENDIX. 



493 



Percentage of Ammonia in Solutions of Different Specific Gravities 

at 15° C. 



Specific gravity. 


Per cent. NH 3 . 


Specific gravity. 


Per cent. NH 3 . 


Specific gravity. 


Per cent. NH 3 . 


0.880 


35.60 


0.925 


20.18 


0.965 


8.59 


0.885 


33.67 


0.930 


18.64 


0.970 


7.31 


0.890 


31.73 


0.935 


17.12 


0.975 


6.05 


0.895 


30.03 


0.940 


15.63 


0.980 


4.80 


0.900 


28.33 


0.945 


14.17 


0.985 


3.55 


0.905 


26.64 


0.950 


12.74 


0.990 


2.31 


0.910 


24.99 


0.955 


11.32 


0.995 


1.14 


0.915 


23.35 


0.960 


9.91 


1.000 


0.00 


0.920 


21.75 











Percentage of Caustic Soda in Solutions of Different Specific Gravities 

at 15° C. 



Specific gravity. 


Per cent. 
NaOH. 


Specific gravity. 


Per cent. 
NaOH. 


Specific gravity. 


Per cent. 
NaOH. 


1.007 


0.61 


1.142 


12.64 


1.308 


27.80 


1.014 


1.20 


1.152 


13.55 


1.320 


28.83 


1.022 


2.00 


1.162 


14.37 


1.332 


29.93 


1.029 


2.71 


1.171 


15.13 


1.345 


31.22 


1.036 


3.35 


1.180 


15.91 


1.357 


32.47 


1.045 


4.00 


1.190 


16.77 


1.370 


33.69 


1.052 


4.64 


1.200 


17.67 


1.383 


34.96 


1.060 


5.29 


1.210 


18.58 


1.397 


36.25 


1.067 


5.87 


1.220 


19.58 


1.410 


37.47 


1.075 


6.55 


1.231 


20.59 


1.424 


38.80 


1.083 


7.31 


1.241 


21.42 


1.438 


39.99 


1.091 


8.00 


1.252 


22.64 


1.453 


41.41 


1.100 


8.68 


1.263 


23.67 


1.468 


42.83 


1.108 


9.42 


1.274 


24.81 


1.498 


46.15 


1.116 


10.06 


1.285 


25.80 


1.514 


47.60 


1.125 


10.97 


1.297 


26.83 


1.530 


49.02 


1.134 


11.84 











494 



THE CHEMISTRY OF PAPER-MAKING. 



Percentage of Sodium Carbonate in Solutions of Different Specific 
Gravities at 15° C. 



Specific gravity. 


Per cent. Na,C0 3 


Per cent. Na 2 C0 3 + 10 H 2 
(soda crystals). 


1.007 


0.67 


1.807 


1.014 


1.33 


3.587 


1.022 


2.09 ' 


5.637 


1.029 


2.76 


7.444 


1.036 


3.43 


9.251 


1.045 


4.29 


11.570 


1.052 


4.94 


13.323 


1.060 


5.71 


15.400 


1.067 


6.37 


1.7.180 


1.075 


7.12 


19.203 


1.083 


7.88 


21.252 


1.091 


8.62 


23.248 


1.100 


9.43 


25.432 


1.108 


10.19 


27.482 


1.116 


10.95 


29.532 


1.125 


11.81 


31.851 


1.134 


12.61 


34.009 


1.142 


13.16 


35.493 


1.152 


14.24 


38.405 



Percentage of Acetate of Lead in Solutions of Different Specific 
Gravities at 15° C. 



Specific gravity. 


Per cent. 

(C 9 H 3 0,) 2 Pb 

+ 3 H" 2 C). 


Specific gravity. 


Per cent. 

(C,H 3 CU,Pb 

+ 3H 2 0. 


Specific gravity. 


Per cent. 
(C,H,0,)oPb 

+ 3'h;o. 


1.0127 


2 


1.1384 


20 


1.2768 


36 


1.0255 


4 


1.1544 


22 


1.2966 


38 


1.0386 


6 


1.1704 


24 


1.3163 


40 


1.0520 


8 


1.1869 


26 


1.3376 


42 


1.0654 


10 


1.2040 


28 


1.3588 


44 


1.0796 


12 


1.2211 


30 


1.3810 


46 


1.0939 


14 


1.2395 


32 


1.4041 


48 


1.1084 


16 


1.2578 


34 


1.4271 


50 


1.1234 


18 











APPENDIX. 



495 



Percentage of Caustic Potash in Solutions op Different Specific 
Gravities at 15° C. 



Specific gravity. 


Per cent. KOH. 


Specific gravity. 


Per cent. KOH. 


1.007 


0.9 


1.252 


27.0 


1.014 


1.7 


1.263 


28.0 


1.022 


2.6 


1.274 


28.9 


1.029 


3.5 


1.285 


29.8 


1.037 


4.4 


1.297 


30.7 


1.045 


5.6 


1.308 


31.8 


1.052 


6.4 


1.320 


32.7 


1.060 


7.4 


1.332 


33.7 


1.067 


8.2 


1.345 


34.9 


1.075 


9.2 


1.357 


35.9 


1.083 


10.1 


1.370 


36.9 


1.091 


10.9 


1.383 


37.8 


1.100 


12.0 


1.397 


38.9 


1.108 


12.9 


1.410 


39.9 


1.116 


13.8 


1.424 


40.9 


1.125 


14.8 


1.438 


42.1 


1.134 


15.7 


1.453 


43.4 


1.142 


16.5 


1.468 


44.6 


1.152 


17.6 


1.483 


45.8 


1.162 


18.6 


1.498 


47.1 


1.171 


19.5 


1.514 


48.3 


1.180 


20.5 


1.530 


49.4 


1.190 


21.4 


1.546 


50.6 


1.200 


22.4 


1.563 


51.9 


1.210 


23.3 


1.580 


53.2 


1.220 


24.2 


1.597 


54.5 


1.231 


25.1 


1.615 


55.9 


1.241 


26.1 


1.634 


57.5 



Per Cent, of Potash Alum (Crystals) in Solutions of Different 
Specific Gravity at 17.5° C. 



Specific gravity. 


Per cent. alum. 


Specific gravity. 


Per cent. alum. 


1.007 
1.010 
1.017 


1 

2 
3 


1.022 
1.027 
1.032 


4 

5 
6 



496 



THE CHEMISTRY OF PAPER-MAKING. 



Density and Composition of Aluminium Sulphate Solutions (Chemically 
Pure). Temperature 15° C. 





a 

3 

o 
<o 
u 
bo 

Q> 

Q 


100 kilos of solution contain kilos. 


100 litres of solution contain kilos. 


u 
&> 

o 
<d 
'o 

Oh 

rjl 


AI 2 3 . 


so 3 . 


CO ^ 

~o 

■3 p. 

m 


n 

-a -~ 
— a> 

■3& 

in 


£ J 

o a 

■s *« 

Oh o 
3 A 

m 


A1 2 3 . 


so 3 . 


CO ■ 

"o 

si 

a o 

O. G) 
■3 0, 
OQ 


c 

- a> 
a 

Oh a 
= ft 
02 


10 . 

.£§ 
« 

•5 " 

C u 
3 * 


1.005 


0.7 


0.14 


0.32 


1.1 


1.0 


0.9 


0.14 


0.33 


1.1 


1 


0.9 


1.010 


1.4 


0.27 


0.64 


2.1 


2.0 


1.8 


0.28 


0.65 


2.2 


2 


1.9 


1.016 


2.1 


0.41 


0.95 


3.1 


2.9 


2.7 


0.42 


0.98 


3.2 


3 


2.8 


1.021 


2.8 


0.55 


1.27 


4.2 


3.9 


3.6 


0.56 


1.31 


4.3 


4 


3.7 


1.026 


3.5 


0.68 


1.59 


5.3 


4.9 


4.6 


0.70 


1.63 


5.4 


5 


4.7 


1.031 


4.2 


0.81 


1.89 


6.3 


5.8 


5.4 


0.84 


1.96 


6.5 


6 


5.6 


1.036 


4.8 


0.94 


2.20 


7.3 


6.7 


6.3 


0.98 


2.28 


7.5 


7 


6.5 


1.040 


5.4 


1.07 


2.50 


8.3 


7.7 


7.2 


1.12 


2.61 


8.6 


8 


7.5 


1.045 


6.1 


1.20 


2.80 


9.3 


8.6 


8.0 


1.26 


2.94 


9.7 


9 


8.4 


1.050 


6.7 


1.33 


3.11 


10.3 


9.5 


8.9 


1.40 


3.26 


10.8 


10 


9.3 


1.055 


7.3 


1.46 


3.40 


11.3 


10.4 


9.7 


1.54 


3.59 


11.8 


11 


10.3 


1.059 


7.9 


1.58 


3.69 


12.2 


11.3 


10.6 


1.68 


3.91 


12.9 


12 


11.2 


1.064 


8.5 


1.71 


3.98 


13.1 


12.2 


11.4 


1.82 


4.24 


14.0 


13 


12.1 


1.068 


9.1 


1.83 


4.27 


14.1 


13.1 


12.2 


1.96 


4.57 


15.1 


14 


13.1 


1.073 


9.7 


1.96 


4.56 


15.1 


14.0 


13.1 


2.10 


4.89 


16.2 


15 


14.0 


1.078 


10.3 


2.08 


4.84 


16.0 


14.8 


13.9 


2.24 


5.22 


17.2 


16 


14.9 


1.082 


10.9 


2.20 


5.12 


16.9 


15.7 


14.6 


2.38 


5.55 


18.3 


17 


15.9 


1.087 


11.4 


2.32 


5.40 


17.8 


16.5 


15.4 


2.58 


5.87 


19.4 


18 


16.8 


1.092 


12.0 


2.44 


5.67 


18.7 


17.4 


16.2 


2.66 


6.20 


20.5 


19 


17.7 


1.096 


12.6 


2.55 


5.95 


19.7 


18.3 


17.0 


2.80 


6.52 


21.5 


20 


18.7 


1.101 


13.1 


2.67 


6.22 


20.5 


19.1 


17.8 


2.94 


6.85 


22.6 


21 


19.6 


1.105 


13.7 


2.78 


6.49 


21.4 


19.9 


18.6 


3.08 


7.18 


23.7 


22 


20.5 


1.110 


14.2 


2.90 


6.76 


22.3 


20.7 


19.3 


3.22 


7.50 


24.8 


23 


21.5 


1.114 


14.7 


3.01 


7.02 


23.2 


21.5 


20.1 


3.36 


7.83 


25.9 


24 


22.4 


1.119 


15.3 


3.13 


7.29 


24.1 


22.4 


20.9 


3.50 


8.16 


26.9 


25 


23.3 


1.123 


15.8 


3.24 


7.55 


24.9 


23.1 


21.6 


3.64 


8.48 


28.0 


26 


24.3 


1.128 


16.3 


3.35 


7.81 


25.8 


23.9 


22.3 


3.78 


8.81 


29.1 


27 


25.2 


1.132 


16.8 


3.46 


8.06 


26.6 


24.7 


23.1 


3.92 


9.13 


30.2 


28 


26.1 


1.137 


17.4 


3.57 


8.32 


27.5 


25.5 


23.8 


4.06 


9.46 


31.2 


29 


27.1 


1.141 


17.9 


3.68 


8.58 


28.3 


26.3 


24.5 


4.20 


9.79 


32.3 


30 


28.0 


1.145 


18.3 


3.79 


8.83 


29.1 


27.1 


25.3 


4.34 


10.11 


33.4 


31 


28.9 


1.150 


18.8 


3.89 


9.07 


30.0 


27.8 


26.0 


4.48 


10.44 


34.5 


32 


29.9 


1.154 


19.2 


4.00 


9.32 


30.8 


28.6 


26.7 


4.64 


10.76 


35.5 


33 


30.8 


1.159 


19.7 


4.11 


9.57 


31.6 


29.3 


27.4 


4.76 


11.09 


36.6 


34 


31.7 


1.163 


20.1 


4.21 


9.82 


32.4 


30.1 


28.1 


4.90 


11.42 


37.7 


35 


32.7 


1.168 


20.6 


4.32 


10.06 


33.2 


30.8 


28.9 


5.04 


11.74 


38.8 


36 


33.6 


1.172 


21.1 


4.42 


10.29 


34.0 


31.6 


29.5 


5.18 


12.07 


39.9 


37 


34.5 


1.176 


21.6 


4.52 


10.53 


34.8 


32.3 


30.1 


5.32 


12.40 


40.9 


38 


35.5 


1.181 


22.1 


4.62 


10.77 


35.6 


33.0 


30.8 


5.46 


12.72 


42.0 


39 


36.4 



APPENDIX. 



497 



Density and Composition of Aluminium Sulphate Solutions {continued). 





a 

3 

a 
o> 

M 

5b . 

Q 


100 kilos of 


solution contain kilos. 


100 litres of solution contain kilos. 


>> 

'> 
a 

So 

u 

s 

"3 

4i 

ft 

02 


Al 2 O s . 


S0 3 . 


M Si 

« o 

.3 t* 

ft 1> 

•gft 

02 


-a -J" 

£ . 

S 1 
a o 

ftCD 

•3ft 

02 


1-1 o 

as 3 
ci a 

■° u 

ft Q> 
3 <* 

m 


A 1,0,. 


so 3 . 


m ■ 

o> 3 

.a u 

&<D 
•— ft 
02 


•£< 

o e 

•3 i. 
ft <D 

■3ft 

02 


^q 
^ _ 

V 3 

•5 *• 

ft Z) 

■3ft 

02 


1.185 


22.5 


4.72 


11.01 


36.3 


33.7 


31.5 


5.60 


13.05 


43.1 


40 


37.3 


1.190 


23.0 


4.82 


11.24 


37.1 


34.5 


32.2 


5.74 


13.38 


44.2 


41 


38.3 


1.194 


23.4 


4.92 


11.47 


37.9 


35.2 


32.8 


5.88 


13.70 


45.2 


42 


39.2 


1.198 


23.8 


5.02 


11.70 


38.6 


35.9 


33.5 


6.02 


14.03 


46.3 


43 


40.1 


1.203 


24.3 


5.12 


11.93 


39.4 


36.6 


34.1 


6.16 


14.35 


47.4 


44 


41.1 


1.207 


24.7 


5.22 


12.16 


40.2 


37.3 


34.8 


6.30 


14.68 


48.5 


45 


42.0 


1.211 


25.2 


5.32 


12.39 


40.9 


38.0 


35.4 


6.44 


15.01 


49.5 


46 


42.9 


1.215 


25.5 


5.41 


12.61 


41.6 


38.7 


36.1 


6.58 


15.33 


50.6 


47 


43.9 


1.220 


25.9 


5.51 


12.83 


42.4 


39.3 


36.7' 


6.72 


15.66 


51.7 


48 


44.8 


1.224 


26.3 


5 r 60 


13.06 


43.1 


40.0 


37.4 


6.86 


15.99 


52.8 


49 


45.7 


1.228 


26.7 


5.70 


13.28 


43.9 


40.7 


38.0 


7.00 


16.31 


53.9 


50 


46.7 


1.232 


27.1 


5.79 


13.50 


44.6 


41.4 


38.6 


7.14 


16.64 


54.9 


51 


47.6 


1.236 


27.5 


5.89 


13.72 


45.3 


42.1 


39.3 


7.28 


16.96 


56.0 


52 


48.5 


1.240 


27.9 


5.98 


13.94 


46.0 


42.7 


39.9 


7.42 


17.29 


57.1 


53 


49.5 


1.244 


28.3 


6.08 


14.16 


46.7 


43.4 


40.5 


7.56 


17.62 


58.2 


54 


50.4 


1.248 


28.6 


6.17 


14.38 


47.5 


44.1 


41.1 


7.70 


17.94 


59.2 


55 


51.3 


1.252 


29.0 


6.26 


14.59 


48.2 


44.7 


41.7 


7.84 


18.26 


60.3 


56 


52.3 


1.256 


29.4 


6.35 


14.80 


48.9 


45.4 


42.3 


7.98 


18.59 


61.4 


57 


53.2 


1.261 


29.8 


6.44 


15.01 


49.5 


46.0 


42.9 


8.12 


18.92 


62.5 


58 


54.1 


1.265 


30.2 


6.53 


15.22 


50.2 


46.7 


43.5 


8.26 


19.25 


63.5 


59 


55.1 


1.269 


30.5 


6.62 


15.43 


50.9 


47.3 


44.1 


8.40 


19.57 


64.6 


60 


56.0 


1.273 


30.9 


6.71 


15.63 


51.6 


47.9 


44.7 


8.54 


19.90 


65.7 


61 


56.9 


1,277 


31.2 


6.80 


15.84 


52.3 


48.6 


45.3 


8.68 


20.23 


66.8 


62 


57.9 


1.281 


31.6 


6.89 


16.04 


53.0 


49.2 


45.9 


8.82 


20.55 


67.9 


63 


58.8 


1.285 


31.9 


6.97 


16.25 


53.7 


49.8 


46.5 


8.96 


20.88 


68:9 


64 


59.7 


1.289 


32.3 


7.06 


16.46 


54.3 


50.5 


47.1 


9.10 


21.20 


70.0 


65 


60.7 


1.293 


32.6 


7.15 


16.66 


55.0* 


51.1 


47.7 


9.24 


21.53 


71.1 


66 


61.6 


1.297 


33.0 


7.23 


16.85 


55.6 


51.7 


48.2 


9.38 


21.86 


72.2 


67 


62.5 


1.301 


33.3 


7.32 


17.05 


56.3 


52.3 


48.8 


9.52 


22.18 


73.2 


68 


63.5 


1.305 


33.7 


7.40 


17.25 


57.0 


52.9 


49.4 


9.66 


22.51 


74.3 


69 


64.4 


1.309 


34.0 


7.49 


17.45 


57.6 


53.5 


49.9 


9.80 


22.84 


75.4 


70 


65.3 


1.312 


34.4 


7.57 


17.65 


58.3 


54.1 


50.5 


9.94 


23.16 


76.5 


71 


66.3 


1.316 


34.7 


7.66 


17.84 


58.9 


54.5 


51.1 


10.08 


23.49 


77.5 


72 


67.2 


1.320 


35.0 


7.74 


18.04 


59.6 


55.3 


51.6 


10.22 


23.81 


78.6 


73 


68.1 


1.324 


35.3 


7.83 


18.23 


60.2 


55.9 


52.2 


10.36 


24.14 


79.7 


74 


69.1 


1.328 


35.6 


7.91 


18.43 


60.8 


56.5 


52.7 


10.50 


24.47 


80.8 


75 


70.0 


1.331 


35.9 


7.99 


18.62 


61.5 


57.1 


53.3 


10.64 


24.79 


81.8 


76 


70.9 


1.335 


36.2 


8.07 


18.81 


62.1 


57.7 


53.8 


10.78 


25.12 


82.9 


77 


71.9 


1.339 


36.5 


8.16 


19.00 


62.7 


58.3 


54.4 


10.92 


25.45 


84.0' 


78 


72.8 



498 



THE CHEMISTRY OF PAPER-MAKING. 



Amount of Lime in Solutions of Milk of Lime of Different Specific 

Gravities. 



Specific gravity. 


Grammes OaO 
in 1 litre. 


Specific gravity. 


Grammes CaO 
in 1 litre. 


Specific gravity. 


Grammes CaO 
in 1 litre. 


1.01 


11.7 


1.10 


126.0 


1.18 


229.0 


1.02 


24.4 


1.11 


138.0 


1.18 


242.0 


1.03 


37.1 


1.12 


152.0 


1.20 


255.0 


1.04 


49.8 


1.13 


164.0 


1.21 


268.0 


1.05 


(32.5 


1.14 


177.0 


1.22 


281.0 


1.06 


75.2 


1.15 


190.0 


1.23 


294.0 


1.07 


87.9 


1.16 


203.0 


1.24 


307.0 


1.08 


100.0 


1.17 


216.0 


1.25 


321.0 


1.09 


113.0 











Percentage of Glycerine in Solutions of Different Specific Gravities. 



Specific gravity. 


Per cent, 
glycerine. 


Specific gravity. 


Per cent, 
glycerine. 


Specific gravity. 


Per cent, 
glycerine. 


1.0123 


5 


1.1320 


50 


1.2265 


84 


1.0245 


10 


1.1455 


55 


1.2318 


86 


1.0374 


15 


1.1582 


60 


1.2372 


88 


1.0498 


20 


1.1733 


65 


1.2425 


90 


1.0635 


25 


1.1889 


70 


1.2478 


92 


1.0771 


30 


1.2016 


75 


1.2531 


94 


1.0907 


35 


1.2106 


78 


1.2584 


96 


1.1045 


40 


1.2159 


80 


1.2637 


98 


1.1183 


45 


1.2212 


82 


1.2691 


100 



Specific Gravity of Different Solutions of Sulphurous Acid in Water. 



Per cent. SO,. 


Specific gravity 
at 15° C. 


Per cent. S0 2 . 


Specific gravity 
at 15° C. 


Per cent. S0 2 . 


Specific gravity 
at 15° C. 


0.5 


1.0028 


4.0 


1.0221 


7.5 


1.0401 


1.0 


1.0056 


4.5 


1.0248 


8.0 


1.0426 


1.5 


1.0085 


5.0 


1.0275 


8.5 


1.0450 


2.0 


1.0113 


5.5 


1.0302 


9.0 


1.0474 


2.5 


1.0141 


. 6.0 


1.0328 


9.5 


1.0497 


3.0 


1.0168 


6.5 


1.0353 


10.0 


. 1.0520 


3.5 


1.0194 


7.0 


1.0377 







APPENDIX. 



499 



Per Cent, of Calcium Chloride in Solutions of Different Specific 
Gravities at 15° C. 



Specific gravity. 


Per cent. 
CaCl 2 . 


Specific gravity. 


Per cent. 
CaCl,. 


Specific gravity. 


Per cent. 

CaCl,. 


1.009 


1 


1.134 


15 


1.277 


29 


1.017 


2 


1.143 


16 


1.288 


30 


1.026 


3 


1.153 


17 


1.299 


31 


1.034 


4 


1.163 


18 


1.310 


32 


1.013 


5 


1.173 


19 


1.322 


33 


1.051 


6 


1.182 


20 


1.333 


34 


1.060 


7 


1.193 


21 


1.344 


35 


1.069 


8 


1.203 


22 


1.356 


36 


1.078 


9 


1.213 


23 


1.368 


37 


1.087 


10 


1.223 


24 


1.380 


38 


1.096 


11 


1.234 


25 


1.392 


39 


1.106 


12 


1.246 


26 


1.403 


40 


1.115 


13 


1.255 


27 


1.411 


40.661 


1.124 


14 


1.266 


28 







1 mother liquor. 



Percentage of Alcohol for Different Specific Gravities. 



Specific gravity 
at 15.5° C. 

(60°F.). 


Per cent, by 
weight of abso- 
lute alcohol. 


Per cent, by 
volume of abso- 
lute alcohol. 


Specific gravity 

at 15.5° C. 

(60° F.). 


Per cent, by 
weight of abso- 
lute alcohol. 


Per cent, by 
volume of abso- 
lute alcohol. 


1.000 


0.00 


0.00 


0.972 


19.67 


24.08 


0.998 


0.79 


0.99 


0.970 


21.31 


26.04 


0.996 


2.28 


2.86 


0.968 


22.85 


27.86 


0.994 


3.41 


4.27 


0.966 


24.38 


29.67 


0.992 


4.62 


5.78 


0.964 


25.86 


31.40 


0.990 


5.87 


7.32 


0.962 


27.21 


32.98 


0.988 


7.27 


9.04 


0.960 


28.56 


34.54 


0.986 


8.64 


10.73 


0.958 


29.87 


36.04 


0.984 


10.08 


12.49 


0.956 


31.00 


37.34 


0.982 


11.62 


14.37 


0.954 


32.25 


38.75 


0.980 


13.15 


16.24 


0.952 


33.47 


40.14 


0.978 


14.82 


,18.25 


0.950 


34.52 


41.32 


0.976 


16.46 


20.24 


0.948 


35.50 


42.40 


0.974 


18.08 


22.18 


0.946 


36.56 


43.56 



500 



THE CHEMISTRY OF PAPER-MAKING. 



Percentage of Alcohol for Different Specific Gravities (continued). 



Specific gravity 

at 15.5° C. 

(90° F.)- 


Per cent, by 
weight of abso- 
lute alcohol. 


Per cent, by 
volume of abso- 
lute alcohol. 


Specific gravity 

at 15.5° C. 

(60° F.). 


Per cent, by 
■weight of abso- 
lute alcohol. 


Per cent, by 
volume of abso- 
lute alcohol. 


0.944 


37.67 


44.79 


0.866 


72.52 


79.12 


0.942 


38.78 


46.02 


0.864 


73.38 


79.86 


0.940 


39.80 


47.13 


0.862 


74.23 


80.60 


0.938 


40.80 


48.21 


0.860 


75.14 


81.40 


0.936 


41.80 


49.29 


0.858 


76.04 


82.19 


0.934 


42.76 


50.31 


0.856 


76.88 


82.90 


0.932 


43.71 


51.32 


0.854 


77.71 


83.60 


0.930 


44.64 


52.29 


0.852 


78.52 


84.27 


0.928 


45.55 


53.24 


0.850 


79.32 


84.93 


0.926 


46.46 


54.19 


0.848 


80.13 


85.59 


0.924 


47.36 


55.13 


0.846 


80.96 


86.28 


0.922 


48.27 


56.07 


0.844 


81.76 


86.93 


0.920 


49.16 • 


56.98 


0.842 


82.54 


87.55 


0.918 


50.09 


58.92 


0.840 


83.31 


88.16 


0.916 


50.96 


58.80 


0.838 


84.08 


88.76 


0.914 


51.79 


59.63 


0.836 


84.88 


89.39 


0.912 


52.68 


60.52 


0.834 


85.65 


89.99 


0.910 


53.57 


61.40 


0.832 


86.42 


90.58 


0.908 


54.48 


62.31 


0.830 


87.19 


91.17 


0.906 


55.41 


63.24 


0.828 


87.96 


91.75 


0.904 


56.32 


64.14 


0.826 


88.76 


92.36 


0.902 


57.21 


65.01 


0.824 


89.54 


92.94 


0.900 


58.05 


65.81 


0.822 


90.29 


93.49 


0.898 


58.95 


66.69 


0.820 


91.00 


94.00 


0.896 


59.83 


67.53 


0.818 


91.71 


94.51 


0.894 


60.67 


68.33 


0.816 


92.44 


95.03 


0.892 


61.50 


69.11 


0.814 


93.18 


95.55 


0.890 


62.36 


69.92 


0.812 


93.92 


96.08 


0.888 


63.26 


70.77 


0.810 


94.62 


96.55 


0.886 


64.13 


71.58 


0.808 


95.32 


97.02 


0.884 


65.00 


72.38 


0.806 


96,03 


97.51 


0.882 


65.83 


73.15 


0.804 


96.70 . 


97.94 


0.880 


66.70 


73.93 


0.802 


97.37 


98.37 


0.878 


67.54 


74.70 


0.800 


98.03 


98.80 


0.876 


68.38 


75.45 


0.798 


98.66 


99.16 


0.874 


69.21 


76.20 


0.796 


99.29 


99.55 


0.872 


70.04 


76.94 


0.794 


99.94 


99.96 


0.870 


70.84 


77.64 


0.7938 


100.00 


100.00 


0.868 


71.67 


78.36 









APPENDIX. 



501 



Per Cent, of Magnesium Chloride in Solutions of Different Specific 
Gravities at 15° C. 



Specific gravity. 


Per cent. 

MgCl 2 . 


Specific gravity. 


Per cent. 
MgCl,. 


Specific gravity. 


Per cent. 
MgCl 2 . 


1.008 


1 


1.113 


13 


1.228 


25 


1.017 


2 


1.122 


14 


1.238 


26 


1.025 


3 


1.131 


15 


1.248 


27 


1.034 


4 


1.140 


16 


1.259 


28 


1.042 


5 


1.150 


17 


1.269 


29 


1.052 


6 


1.159 


18 


1.279 


30 


1.060 


7 


1.169 


19 


1.290 


31 


1.068 


8 


1.178 


20 


1.301 


32 


1.077 


9 


1.188 


21 


1.312 


33 


1.086 


10 


1.198 


22 


1.323 


34 


1.095 


11 


1.208 


23 


1.334 


35 


1.104 


12 


1.218 


24 







BIBLIOGRAPHY. 



Archer, T. C. — British Mfg. Industries. Vol. 8. Manufacture of Paper. 
— Ibid., Vol. 15. The Industrial Classes and Industrial Statistics. Paper 
and Paper-making. 
Arxot. — Technology of the Paper Trade (Cantor Lecture, Society of Arts). 

London, 1877. 
Briquet, C. M. — Papiers et filigranes des archives de Genes. 1154-1700. 

Geneva, 1888. 
Christy, Thomas. — New Commercial Plants and Drugs, No. 6, Part L, 

Fibres. London, 1882. 
Clapperton, George. — Practical Paper-making. London, 1894. Crosby 

Lockwood & Son. 
Cross, C. F. — Report on Miscellaneous Fibres. London, 18S6. William 

Clowes & Sons. 
Cross and Bevan. — Report on Pictet-Brelaz Process. London, 1887. E. & 
F. N". Spon. 
Cellulose. London, 1885. George Kenning. 
Chemistry of Hypochlorite Bleaching. Jour. Soc. Chem. Ind., May 31, 

1890. 
Chemistry of Bast Fibres. Manchester, 1880. Palmer & Howe. 
Reports on Hermite Process. London, 1886. 

A Text-book of Paper-making. London, 1888. E. & F. N. Spon. 
Report on Indian Fibres and Fibrous Substances. London, 1887. E. & F. 
N. Spon. 



502 THE CHEMISTRY OF PAPER-MAKING. 

Davis, Charles Thomas. — The Manufacture of Paper. Phila., 1886. Henry 

Carey Baird & Co. 
Dunbar, J. — The Practical Paper-maker. London, 1881. 
Forestry and Forest Products. Edinburgh, 1884. 
Garcon, Jules. — Bibliographie de la Technologie Chimique des Fibres 

Textiles. Paris, 1893. Gauthier-Vi liars et Fils. 
Griffin, Martin L. — Remarks on Chemistry of Sulphite Processes. Trans. 

Amer. Soc. C. E., 417. 1889. 
Herzberg, W. — Papier-Priifung. Berlin, 1888. Julius Springer. 
Hofmann, Carl. — A Treatise on Paper-making. Phila., 1873. New and 
much enlarged edition, Howard Lockwood & Co., New York. (In press.} 
Hohnel, Franz von. — Die Mikroskopie der technish verwendeten Faserstoffe. 

Vienna, 1887. Hartleben. 
Hoyer, Egbert. — Fabrikation des Papiers. Brunswick, 18S6. F. Vieweg & 

Sohn . 
Jagenberg, Ferdinand. — Die Thierische Leimung fiir endloses Papier. 

Berlin, 1878. Julius Springer. 
Japanese Papers. — Boston Public Library. * 5024-18 contains 81 specimens 

of plain and tinted papers ; * 5024-20 has 64 specimens of ornamented 

papers. 
Le Normand, L. S. — Manuel du Fabricant des Papiers. Paris, 1834. 
Michaelis, Major O. E. —Lime Sulphite Fibre Mfg. in U. S. Trans. Amer. 

Soc. C. E., 417. 1889. 
Mierzinski, S. — Handbuch der Papier-fabrikation. Vienna, 1886. 
Muller, Dr. A. — Die Bestimmung des Holzschliffes im Papier. Berlin, 

1887. Julius Springer. 
Muller, Dr. L. — Die Fabrikation des Papiers. Berlin, 1877. Julius 

Springer. 
Muller, Hugo. — Die Pflanzenfaser. Leipzig, 1873. 
Murray, J. — Practical Remarks on Modern Paper. Edinburgh, 1829. 
Normal-Papier. — Pub. by Die Papier-Zeitung. Berlin, 1891. 
Parkinson, R. — A Treatise on Paper. Preston, 1886. 
Patents, British. — Abridgements of specifications relating to Paper. 1636- 

1876. 
Planche, G. — LTndustrie de la Papeterie. Paris, 1853. 
Proteaux. — The Manufacture of Paper and Boards. Phila., 1873. 
Routledge, Thomas. — Bamboo as a Paper-making Material. London, 1875. 

E. & F. N. Spon. 
Sadlter, Samuel P. — Industrial Organic Chemistry, pp. 262-291. Phila., 

1892. J. B. Lippincott Co. 
Sargeant, Charles S. — Forest Trees of North America. Tenth U. S. Census. 
Schubert, Max. — Die Cellulosefabrikation . Berlin, 1892. Fischer & 

Heilmann. 
Tomlinson. — The Manufacture of Paper. 
Vetillart. — Etudes sur les Fibres Vegetales. Paris, 1876. 
Watt, Alex. — The Art of Paper-making. London, 1890. 
Wiesner, Dr. Julius. — Die Mikroscopische Untersuchung des Papiers. 

Vienna, 1887. 



INDEX, 



REFERENCES ARE TO PAGES. 



Absorption apparatus, 203. 
Behrend, 223. 
Catlin, 217. 
Ekman, 210. 
Frank, 223. 
Francke, 218. 
McDougall, 214, 216. 
Mitscherlicb, 205. 
Nemethy, 220. 
Partington, 215. 
Ritter-Kelluer, 

tank apparatus, 212. 

towers, 218. 
tower systems, 204. 
Wendler-Spiro, 221. 
Wheelwright, 215. 
Accent of chemical terms, 165, 468. 
Acetate of alumina, 77. 
lead, 92, 397. 

density of solutions, 494. 

Acetates, analysis of, 397. 

Acetic acid, analysis, 357. 

density of solutions, 492. 

use in bleaching, 293. 

Acid, acetic, analysis, 357. 

density of solutions, 492. 

use in bleaching, 293. 
alkali-cellulosexanthic, 470. 
antimouic, 89. 
arsenic, 61. 
arsenious, 60. 
benzoic, 139. 
boracic, 57. 
boric, 57. 
carbonic, 32. 
carminic, 322. 

cellulose-thiosulphocarbonic, 468. 
chloric, 54. 
chlorous, 54. 
cinnamic, 139. 
cyanhydric, 35. 
free, action on cellulose, 282. 

in alum, 311. 
det. of, 380. 

in paper, 437. 

in sulphite liquor, 209, 225. 
hydrochloric, 49. 

analysis, 355. 

density of solutions, 491. 



Acid, hydrofluoric, 56. 
hypochlorous, 51. 
hyposulpburous, 44. 
muriatic, 49. 
analysis, 355. 
density of solutions, 491. 
nitric, 30. 

analysis, 356. 
density of solutions, 490. 
Nordhausen, 47. 
oxalic, analysis, 358. 

density of solutions, 483. 
perchloric, 55. 
polythiouic, 47. 
pyroligneous, analysis, 357. 
sulphites, 41. 
sulphuric, 45. 
analysis, 353. 
density of solutions, 488. 
in burner gas, 197. 
in paper-testing, 443. 
prep, of different strengths, 488. 
in sulphite liquor, 414. 
sulphurous, 40. 

action upon life, 274. 
action upon throat and lungs, 274. 
analysis, 412. 
density of solutions, 498. 
sylvic, 139. 
thionic, 47. 
thiosulphuric, 45. 
waters, 334. 
Acids, analysis of, 353. 

definition, 15. 
Adansonia, composition of bast, 128. 
Agalite (Fig. 69), 316, 440. 
Agate, 58. 
Agave, 129. 
Air, 29. 

in wood cells, 137. 
Air-dry pulp, 449. 

calculation of, 451. 
Alabaster, 73. 
Alcohol, 106. 

density of solutions, 499. 
Alfa, 131. 
Algae, 331-337. 
Alkali, analysis, 359. 
by electrolysis, 460. 



503 



504 



INDEX. 



Alkali, cellulose, 468. 

manufacturing, 65. 

metals, 63. 

in soda pulp, 289. 
Alkaline earths, analysis, 359. 

metals of, 69. 
Aloe fibre, 129. 
Alternating current, 456. 
Alum, 77. 

ammonia, 78. 

potash, 78. 

density of solutions, 495. 
Alum (sulphate of alumina) , 309. 

analyses of, 310. 

analysis of, 375. 

density of solutions, 496, 497. 

free acicl, det. of, 380. 

manufacture of, 77. 

moisture in, 382. 

preservative effect on size, 303. 

sizing test for, 380. 
Alumina, 76. 
Aluminate of soda, 307. 
Alumine, fibrous, 317. 
Aluminum, 76. 

acetate, 77. 

bleach liquor, 295. 

chloride, action on cellulose, 282. 

hydrate, 77. 

hydroxide, 77. 

oxide, 76. 

sulphate, see Alum. 
Amalgams, 63, 97. 
Amethyst, 58. 

color of, 82. 
Ammonia, 30, 69. 

analysis of, 361. 

density of solutions, 493. 

water, 30, 69. 
Ammonia alum, 77. 
Ammonium, 68. 

hydrate, analysis, 361. 

density of solutions, 493. 

hydroxide, 69. 

sulphate, 69. 
Ampere, 454, 455. 

law of, 7. 
Amyloid, 107. 
Analysis, chemical, 348. 

volumetric, 353. 
Anion, def., 453. 
Anode, def., 453. 

use of gas carbon for, 460. 
Andreoli process, 4(50. 
Anatase, 86. 
Anhydrides, def., 16. 
Anhydrite, 73. 
Aniline colors, 325. 

analysis of, 401. 

red, 325. 

sulphate, 445. 



Aniline sulphate for paper-testing, 443. 
Animal size, 301. 

first use of, 434. 
Annaline, 317. 
Autichlor, 281,283. 

analysis of, 395. 

Hosford's, 284. 
Antimonic anhydride, 89. 

chloride, 88. 

sulphide, 88. 
Antimonous antimouate, 88. 

chloride, 88. 

hydride, 88. 

oxide, 88. 

oxychloride, 88. 

sulphide, 88. 
Antimony, 88. 

group, 88. 
Apatite, 73. 

Apparatus for analysis, 348. 
Aqua ammonia, 30. 

density of solutions, 493. 
Aqua fortis, 30. 

density of solutions, 490. 
Arithmetic, chemical, 18. 
Argentic oxide, 95. 
Argentous oxide, 95. 
Arsenic, 60. 

acid, 61. 

in aniline colors, 60. 

in hides, 303. 

in wall paper, 60. 
Arsenide of cobalt, 83. 
Arsenite of soda, preservative for size, 303. 
Arsenious acicl, 60. 
Artificial silk, 111. 
Asbestos, 74. 
Ash in paper, 437. 

in pulp, 438. 
Aspen, 145. 
Atomic theory, 5. 

weights, 8. 
table of, 486. 
Atoms, 5. 
Auramine, 326. 

Bacteria, 338. 

iron, 332. 

jelly, 338. 
Baeyer, cellulose and chlorine, 113. 
Bagasse, 132. 
Baking soda, 65. 
Balsam, 143. 
Balsams, 138, 139. 
Bamboo, 132. 
Barium, 70. 

hydrate, 70. 

hydroxide, 70. 

oxide, 70. 

peroxide, 70. 

sulphate, 70. 



INDEX. 



505 



Bark, 140. 

coloring matter of, 141. 

mulberry, 128. 

tannin, 141. 
Baryta, caustic, 70. 
Bases, def., 15. 

det. of in sulphite liquors, 414. 
Basic alum, 312. 

lead chromate, 92. 
Bass wood, 147. 
Bast fibres, 121. 

characteristics of, 122. 
Bauxite, 77. 
Beadle, cellulose, derivatives, 4G8. 

formula for size, 305. 
Beaume hydrometer, 482, 483. 
Becquerel, electrolysis of chlorides, 457. 
Beech, 146. 
Belgian flax, 124. 
Benzoic acid, 139. 
Berlin blue, 400. 
Beryllium, 75. 

Bevan, cellulose derivatives, 468. 
Bibliography, 501. 
Bicarbonate, ferrous, 81. 

of soda, 371. 
Bichromate of potash, 85, 398. 

of soda, 398. 
Birch, paper, 147. 

white, 147. 
Bismuth, 89. 

nitrate, 89. 

terchloride, 89. 
Bisulphide of carbon, 48. 

action on cellulose, 408. 
Bisulphites, 41. 
Bisulphite of lime, 184. 

liquor, analyses of, 226-228. 
analysis. 412. 
mfg., 190. 

of magnesia, 184. 

of soda, 184. 
Black ash, analysis of, 370. 
Black liquor, analysis of, 165. 
Black spruce, 142. 
Black willow, 148. 
Blast furnace, 80. 

lamp, Russian, 351. 
Bleach, consumed by water, 332. 

liquid chlorine, 296. 

liquor, 279. 

aluminum, 295. 
Crouvelle's, 295. 
magnesium, 294. 
Ramsey's, 295. 
Wilson's, 295. 
zinc, 295. 

oxygen, 298. 

ozoue, 298. 

removal from cellulose, 282. 

sulphurous acid, 299. 



Bleaching, 275. 

acid, use of in, 292. 

chlorination of cellulose in, 285. 

Cloudman process, 290. 

ground wood, 294. 

Hermite process, 457. 

hot, 281. 
Bleaching jute, 294. 

rags, 281. 

wood fibre, 281. 
Bleaching-powder, 275. 

analysis of, 391. 

composition of, 278. 

consumption of, 280. 

deterioration of, 277. 

introduction of, 276. 

manufacture of, 52. 
by electrolysis, 460. 

preparation of solution, 279. 

properties, 276. 

strength of, 277. 
Bleaching-salt, Varrentrapp's, 295. 
Blotting-paper, capillary power, 436. 
Blowpipe, oxyhydrogen, 28. 
" Blue Billy," 40. 

composition of, 177. 
Blue dyes, 326. 

stone, 93, 384. 

vitriol, 93. 
Boiler, sulphite, see Digester. 

vomiting, 157. 
Boiler scale, 333,412. 

composition of, 334. 
Boiling-point of water, 165. 
Boiling rags, 151. 

Boiling wood by sulphite process, 250. 
Boracic acid, 57. 
Borax, 57, 65. 
Boric acid, 57. 
Boron, 57. 
Boron fluoride, 57. 
Bottger and Otto, discovery of guncotton, 

108. 
Brandt, electrolysis of sea-water, 457. 
Britannia metal, 88. 
Bromine, 55. 
Brookite, 86. 
Bronze, 86. 

digesters, 239. 
Brown dyes, 326. 
Buckeye^ 148. 

Buddeus, waste sulphite liquors, 271. 
Burette, 349. 
Burgess, Hugh, electrolysis of chlorides, 

457. 
Burnett's disinfecting solution, 75. 
Burning of pulp, 252. 

Cadmium, 75. 
Caesium, 68. 
Calamine, 74. 



506 



INDEX. 



Calcium, 71. 
carbonate, 72. 

see also Carbonate of Lime, 
chloride, 72, 390. 

density of solutions, 499. 
in paper, 437. 
in pulp, 283. 
hydrate, 71, 72. 
analysis of, 362. 
density of milk of lime, 498. 
hydroxide, 71. 
hypochlorite, 391. 

see also Bleaching-powder. 
hyposulphite, 45. 
Carbon, 31. 

bisulphide, 48. 

action on cellulose, 468. 
dioxide, 32. 
monoxide, 32. 
and nitrogen, 35. 
and oxygen, 32. 
and sulphur, 48. 
Carbonate of iron, 80. 
of lime, 72. 
analysis, 374. 

formation in causticizing, 174. 
in towers, 204. 
water, 333. 
of magnesia, 74. 
analysis, 374. 
in water, 330. 
of potash, 64. 
analysis, 373. 
Calcium oxide, 71, 72. 
analysis, 362. 
see also Lime, 
phosphate, 73. 
sulphate, 73. 

filler for paper, 316-318. 
see also Lime, Sulphate of. 
sulphite, 42. 

use as antichlor, 284. 
in pulp, 270. 

see also Lime, Sulphite of. 
thiosulphate, use as antichlor, 285. 
Calomel, 97. 
Cambium layer, 135. 
Canary paste, 398. 
yellow, 85, 398. 
Capacity, measures of, 478. 
Carbohydrates, 34, 104. 
Carbonate of soda, 65. 
analysis, 367. 
causticizing, 173-175. 
density of solutions, 494. 
mfg., 65. 

use in treating picker seed, 156. 
rag-boiling, 153. 
sulphate process, 178. 
sulphite process, 230. 
of zinc, 75. 



Carbonate of zinc, analysis, 375. 
Carbonates, 33. 
analysis, 367. 
Carbonic acid, 32. 
auhydride, 32. 
Carbonizing wool, 114. 
Carmichael process, 460. 
Carminic acid, 323. 
Carnelian, 58. 
Casein sizing, 307. 
Casserole, 350. 
Cassiterite, 86. 
Cast-iron digester, 232. 
Cathion, def., 453. 
Cathode, def., 453. 

use of iron for, 460. 
Caustic ash, analysis, 369. 
baryta, 70. 
potash, 64. 

analysis, 361. 
soda, 64. 

analysis, 359. 
density of solutions, 493. 
Caustic soda, mfg., 65. 
use in making size, 304. 

preventing boiler-scale, 335. 
soda process, 161. 
sulphate process, 179. 
treating rags, 155. 
straw, 159. 
Celestine, 47. 
Cellulose, 103. 

and chlorine, 112. 

oxygen, 113. 
effect of heat upon, 115. 
fermentation of, 115. 
Mercerized, 115. 
processes for isolating, 151. 
Cellulose acetate, 108. 
benzoate, 470. 
nitrates, 109. 
thiocarbonates, 468. 
Celsius thermometer, 479. 
Cement, 72. 
Cement linings, 246. 
Curtis & Jones, 250. 
Kellner, 246. 
Russell, 247. 
Wenzel, 246. 
Centigrade thermometer, 479. 
Century plant, fibre of, 129. 
Cerium, 79. 
Chalk, analysis, 374. 
Chalybeate waters, 81. 
Chemical changes, def., 3. 
Chemistry, def., 3. 

organic, def., 35. 
Chestnut, 148. 
Chili saltpetre, 65, 396. 
China grass, 128. 
Chloric acid, 54. 



INDEX. 



507 



Chloride of aluminum, action on cellulose, 
282. 

of calcium, 390. 

density of solutions, 499. 

ferric, 391. 

of gold, 98. 
" Chloride of Lime," 275. 

see also Bleaching-powder. 
Chloride of magnesium, 389. 
in Hermite process, 457. 
in water, 333. 

of potash, 64. 

of platinum, 98. 

of sodium, 65. 
analysis of, 386. 
density of solutions, 482. 

of zinc, 75. 
Chlorides, action on cellulose, 282. 

analysis of, 386. 

in paper, 437. 
Chlorine, 49. 

action upon coloring matters, 276. 

liquid, 296. 

mfg. by electrolysis, 453. ' 
Chlorine and cellulose, 112. 

and hydrogen, 49. 

and nitrogen, 55. 

and oxygen, 50. 

and sulphur, 55. 
Chlorine, anhydrides of, 51. 

dioxide, 51. 

hydrate, 49. 
Chlorates, 54. 

Chlorinated compounds in bleached cellu- 
lose, 285. 
Chlorinated soda, 394. 
Chlorites, 54. 
Chlorophyll, 117. 
Chlorous acid, 54. 
Choke-damp, 32. 
Chrome yellow, 321, 398. 
Chromate of lead, 85, 92, 321, 398. 

of potassium, 84. 
Chromates, analysis of, 398. 
Chromium, 84. 

compounds, 84. 
Cinnabar, 37. 

Cinnamic acid, in resins, 139. 
Clark process, 335, 406. 
Classification of papers, 420. 
Clay, 58, 77. 

composition of, 316. 

determination of, in paper, 439. 

use as paper-filler, 315. 
Clay iron-stone, 80. 
Cloudman's bleaching apparatus, 290. 
Coal-tar colors, 325. 
Cobalt, 83. 

compounds of, 83. 
Cochineal, 322. 
Cocoanut fibre, 128. 



Cohesion, 6. 
Coir fibre, 128. 
Coke, 31. 
Collodion, 111. 
Colophony, 139. 
Color furnishes, 328. 

of paper, 320. 

of pulp, 266. 

of water, 330. 
Coloring, 320. 
Coloring matter of bark, 141. 

of cotton, 121. 

of knots, 141. 
Colors, ash of mineral, 440. 

substantive, 320. 
Columbium, 90. 
Combined rosiu, 419. 
Combustion, 26, 33. 

spontaneous, 26. 
Compounds, 7, 10. 

Condensed water in sulphite process, 255. 
Coniferous trees, wood of, 134. 
Connecticut River, color of water, 331. 
Conservation of energy, 3. 
Continuous current, 455. 
Copper, 92. 

pyrites, 198. 

sulphate, 384. 
Copperas, 81, 385. 
Coprolites, 73. 
Cork, 141. 
Corundum, 76. 
Cotton, 121. 

threads, strength of, 289. 

waste, 157. 
Cottonwood, 145. 
Craney process, 460. 
Cream of tartar, 64. 
Crenothrix, 332. 
Crocker process, 230. 

Cross and Bevan, action of chlorine on 
cellulose, 112. 

exam, of fibres, 123, 124. 

lignification, 118. 
Cross, Bevan, and Beadle, new cellulose 

derivatives, 468. 
Crouvelle's bleaching-liquor, 295. 
Crown filler, 317. 
Cryolite, 57, 77. 
Current, electric, 454. 
Current efficiency, 454. 
Curtis & Jones lining, 250. 
Cutton process, 460. 
Cyanhydric acid, 35. 
Cyanogen, 35. 
Cypress, 146. 

Dalton, atomic theory, 5. 
De Chardonnet, artificial silk, 111. 
Definite proportions, 9. 
Deliquescence, 64. 



508 



INDEX. 



Density of woods, 137. 

Dervaux filter, 344. 

Desiccator, 351. 

Dextrin, 106, 114. 

Diamond, 31. 

Diaphragm, use in electrolysis, 460. 

Didymium, 79. 

Difference of potential, 454. 

Digesters, 162, 232. 

bronze, 239. 

cement-lined, 246. 

emptying of, 260, 263. 

enamel-lined, 243. 

experimental, 269. 

lead-lined, 232. 

Mitscherlich, 242. 

Salomon-Briingger, 243. 

valves for, 240. 
Dinitrocellulose, 110. 
Dirt in paper, 423. 

in pulp, 267. 
Discs, use of in Mitscherlich process, 190. 
Dithionates, 47. 
Dolomite, 227. 
Drying, loft, 303. 
Duramen, 136. 

Durin, cellulosic fermentation, 116. 
Dyes, 320-322. 

dilutions of, 327. 

testing of, 326. 

Earth metals, 76. 

Eau de Javelle, 296, 394. 

de Labarraque, 296. 
Eder, nitrogen in pyroxylins, 110. 

prep, of cellulose penta-nitrate, 110. 
Edge-runner for working straw, 161. 
Ekman furnace, 194. 
modified, 195. 
lining, 237. 
process, 185. 
towers, 210. 
Electric bleaching, 452. 
Electricity, conduction by liquids, 4"2. 
Electric current, analogy to flowing water, 
454. 
effect of, 452. 
Electrical units, 454. 
Electrolysis, 453. 
conditions of, 456. 
theory of, 456. 
Electrolytes, def., 453. 
Electrolytic processes, 452. 
efficiency of, 462. 
general features of. 460. 
Electrolyzer, Her mite, 457. 
Electromotive force, 454. 
Elements, chemical, 5, 7. 
metallic, 62. 
non-metallic, 25. 
table of, 486. 



Elements of wood, 133. 
Emerald, 75. 
Emery, 76. 
E. M. F., 454. 

Energy, conservation of, 3. 
Engine sizing, 304. 
English test for alkali, 360. 
Eosin, 326. 
Epsom salts, 47. 
Equations, 17. 
Equivalents, 13. 
Erbium, 79. 
Esparto, 131. 

treatment of, 157. 
Euchlorine, 51. 
Evaporation, multiple effect, 166. 

open pan, 165. 
Evaporator, Gaunt, 169. 

Porion, 172. 

Yaryan, 166. 
Examples in chemical arithmetic, 19. 
Expansion of lead, 232. 
Experimental digester, 269. 

Fahrenheit's thermometer, 479. 
Fermentation, decomposition of cellulose 
by, 115. 

formation of cellulose by, 116. 
Ferric chloride, 81. 

nitrate, 397. 

oxide, 81. 

salts, def., 15. 
Ferricyanide of potassium, 35. 
Ferrocyanide of potassium, 35. 
Ferrous bicarbonate, 81. 

salts, def., 15. 

sulphate, 385. 
Fibres, 117. 

bast, 121. 

chemical examination, 124. 

derived from whole stems or leaves, 129. 
from wood, 132. 

fungoid growth on, 269. 

microscopical examination, 441. 

staining effects, 443. 

standard mixtures, 444. 
Fibrous alumine, 317. 

tests for in paper, 439. 
Fillers, mineral, 314. 
Filter, Dervaux, 344. 

gravity, 338. 

New York, 341. 

pressure, 341. 

Warren, 338. 
Filter paper, analysis of, 287. 
Filter-beds, 337. 
Filtration, 336. 
Filaments, 123. 
Fir, white, 143. 
Flax, 124. 
Flax, New Zealand, 127. 



INDEX. 



509 



Flint, 58. 

Flint glass, 92. 

Flowers of sulphur, 36. 

Fluoride of boron, 57. 

Fluorine, 56. 

Fluorspar, 56. 

" Fool's gold," 38. 

Fracture length of paper, 425. 

how calculated, 426. 
Frank, Dr., action of waste sulphite liquors 
on animal life, 273. 

sulphite liquor apparatus, 223. 
Free acid in alum, 311. 

in sulphite liquor, 208. 

rosin, determination of, 418. 
Freiberg pyrites burner, 198. 
French white, analysis of, 374. 
Fuchsine, 325. 
Fuel value of woods, 138. 
Fungoid growth in hbre, 269. 

Galena, 37, 91. 

Gallium, 94. 

Gas-cooler, Wheelwright, 203. 

Gas pressure, 7. 

in sulphite process, 252. 
Gas recovery, 261. 
Gelatine, 302. 

Gemmell, moisture in pulp, 451. 
German silver, 84. 
Girard, hydration of cellulose, 114. 
Gladstone, action of soda upon cellulose, 

115. 
Glass, 58. 
Glauber's salt, 65. 
Glucinum, 75. 
Glucose, 106, 114. 
Glue, 302. 

Glycerine, density of solutions, 498. 
Godeffroy, det. of ground wood, 446. 
Gold, 98. 

Goodale, bast-fibres, 122. 
Graham digester, 238. 
Graphite, 31. 
Graphic symbols, 14. 
Gravity filters, 338. 
Gray pine, 142. 
Green dyes, 326. 

vitriol, 81. 
Greenwood process, 460. 
Griffin, Martin L., moisture in pulp, 450. 
Grit in paper-fillers, 315. 
Ground wood, bleaching of, 294. 

sampling, 447. 

tests for, 445. 
Growth of wood, 135. 
Gum resins, 138. 
Gum, sweet, 145. 
Gums, 120. 
Guucotton, 109. 
Gypsum, 47, 73. 



Gypsum paper-filler, 317. 

det. of, 439. 
Hackmatack, 144. 
Haermatite, 80. 
Halogens, 57. 

compounds of, 57. 
Hard water, 72, 329. 
Hardness, test for, in water, 403. 
Heart wood, 136. 
Heat, 6. 

latent, 7. 

relations of atoms to, 8. 

specific, 7. 

unit of, 7. 

units developed by combustion, 33. 
Heavy spar, 47, 70. 
" Heavy lead ore," 91. 
Hemlock, 144. 
Hemp, 126. 

sisal, 129. 

sunn, 127. 
Henequin, 129. 
Hermite process, 457. 
Herzberg, ash in pulps, 438. 

plate of fibres, 132. 
Hewitt and Mond, causticizing process, 175. 
Hexanitrocellulose, 110. 
Hohnel, lignin reactions, 445. 
Holland and Richardson process, 460. 
Horse power, electrical, 456. 
Hosford's antichlor, 284. 
Hydrate of aluminum, 77. 

of calcium, 71. 

of magnesium, 74. 
Hydrates, def., 15. 
Hydraulic lime, 72. 
Hydrocarbons, 31. 
Hydrocellulose, 114,437. 
Hydrochloric acid, 49. 

analysis of, 355. 

density of solutions, 491. 

use in bleaching, 292. 
Hydrofluoric acid J 56. 
Hydrogen, 27. 

and chlorine, 49. 

peroxide, 29. 
mfg., 70. 
use as antichlor, 285. 

sulphide, 38. 
Hydrolysis, def., 182. 
Hydrometer, Beaume', 482, 483. 

Twaddle's, 484. 
Hydroxide of alumina, 77. 

of zinc, 74. 
Hypochlorite of aluminum, 295. 

of calcium, 275, 391. 

of magnesium, 294, 394. 

of potash, 296, 394. 

of soda, 296, 394. 

of zinc, 295. 
Hypochloi-ites, prep, by electrolysis, 452. 



510 



INDEX. 



Hypochlorous acid, 51, 292. 
Hyposulphite of soda, 45; 283. 
Hyposulphurous acid, 44. 

Indian red, 400. 

Indium, 94. 

Injectors for transferring liquor, 231. 

Iodine, 56. 

solution for paper-testing, 443. 
Ion, def., 453. 
Intensity currents, 455. 
Iridium, 100. 
Irish flax, 124. 
Iron, 80. 

in alum, 311. 

bacteria, 332. 

pyrites, 198. 

wood, 138. 
Isinglass, 302. 
Italian hemp, 126. 

Javelle water, 394. 

Jung and Lindig lining, 245. 

Jute, 125. 

bleaching of, 294. 

treatment of, 293. 
Kaolin, 58. 
Kellner, cement lining, 246. 

filtering-tower, 201. 

sizing, 313. 
Kellogg lamp, 351. 
Kier, the Mather, 153. 
Knofler oven, 449. 
Knots, 140. 

removing from wood, 189. 
Kupfer-nickel, 84. 

Labarraque's solution, 394. 
Lampblack, 31. 
Lanthanum, 79. 
Larch, 144. 
Latent heat, 7. 
Lavoisier, 3. 
Law of Ampere, 7. 

of definite proportions, 9. 
of multiple proportions, 12. 
Ohm's, 455. 
Lead, 91. 

action of acids upon, 233. 
burning, 241. 
linings, 232. 
Ekman, 237. 
Francke, 234. 
Graham, 238. 
Makin, 235. 
Mitscherlich, 242. 
Partington, 234, 236. 
Ritter-Kellner, 237. 
Russell, 235. 
Springer, 236. 
Wheelwright, 238. 



Lead acetate, 92, 397. 

density of solutions, 494. 

chromate, 85, 92. 
testing, 398. 
use in coloring paper, 321. 

sugar of, 92, 397. 

density of solutions, 494. 
Leblanc process, 65. 
Length, measures of, 478. 
Leonhardi's test for sizing, 436. 
Le Sueur and "Waite process, 460. 
Liber-fibres, 123. 
Light, action on rosin size, 306. 
Lignified fibre, tests for, 445. 
Lignification, 118. 
Lignin, 118. 
Lignireose, 119. 
Lignite, 31. 
Lignone, 119. 
Lignose, 119. 
Lime, 71. 

analysis of, 362. 

composition of, for causticizing, 174. 

for rag-boiling, 152. 

for sulphite liquor, 227. 

det. of in sulphite liquor, 414. 

hydraulic, 72. 

milk of, 71. 
density, 498. 

reclaimer, 175. 

water, 71. 
Lime, carbonate of, 72. 
analysis, 374. 
in water, 333. 

sulphate of, 73, 191. 

sulphite of, 191, 229, 253. 
Limestone, 72. 

analysis of, 374. 

use in tanks, 212. 

in towers, 204. 
Linen, 124. 

Liquor-making, sulphite, 190. 
Litharge, 91. 
Lithium, 68. 
Loading paper, 314. 
Locust, 148. 
Lunar caustic, 96. 

Mactear, tabulated view of alkali mfg.,67. 
Magenta, 325. 
Magnesia, 74. 

analysis, 365. 

bleach liquor, 294. 

det. of in sulphite liquors, 414. 

use in Ekman process, 187, 210. 
Magnesite, analysis, 374. 
Magnesium, 73. 

carbonate, analysis, 374. 

chloride, 389. 

density of solutions, 501. 
electrolysis of, 458. 



INDEX. 



511 



Magnesium hydrate, 74, 365. 

hypochlorite, 294, 394. 
by electrolysis, 458. 

oxide, 74, 187,' 210. 

silicate, 74. 

use as paper-filler, 316, 440. 

sulphate, 74, 384. 
Magnetic iron ore, 80. 

metals, 79. 
Magnetite, 80. 
Makin lining, 235. 
Malachite green, 326. 
Manganese, 82. 
Manganite, 82. 
Manila, 126. 
Maple, silver, 146. 
Marble, analysis, 374. 
Marsh gas from cellulose, 116. 
Mass, def., 4. 
Mather Kier, 153. 
Matter, 3. 

conservation of, 3. 

properties of, 5. 

states of, 6. 
Mauvein, 325. 
McDougall, digester lining, 235. 

liquor apparatus, 212, 217. 
Measures, metric system, 4, 478. 
Meerschaum, 74. 
Mercerized cellulose, 115. 
Mercury, 97. 

compounds of, 97. 
Merrimac River, color of water, 331. 
Metals, 62. 

alkali group, 63. 

antimony group, 88. 

of alkaline earths, 69. 

earth, 76. 

iron group, 79. 

lead group, 90. 

magnesium group, 73. 

magnetic, 79. 

noble, 95. 

silver group, 95. 

tin group, 85. 
Metantimonic acid, 89. 
Methyl violet, 326. 
Metric system, 478. 
Microscope, 441. 
Microscopical examination of fibres, 441. 

of paper-fillers, 314. 
Milk of lime, 71. 

density of, 498. 
Millon's reagent, test for animal size, 432. 
Mineral colors, 321, 398. 
Mineralization of cell-wall, 117. 
Minium, 91. 
Mitscherlich process, digester, 242. 

gas recovery, 262. 

boiling, 256. 

pulp, 267. 



Mitscherlich process, pyrites burner, 199. 

stamp mill, 263. 

sulphur furnace, 196. 

tower system, 205. 
Mitscherlich sizing process, 313. 
Mixtures and compounds, 10. 
Moisture in pulp, 446. 
Molecules, 5. 
Molybdenite, 87. 
Molybdenum, 87. 

" Money value " test for dyes, 402. 
Monosulphite of calcium, formation of, 
228, 253. 

incrustation, 229, 253. 

removal of, 230. 
Mordants, 320. 
Mortars, 72. 
Mosaic gold, 86. 
Mulberry tree, 128. 
Mulder, formation of glucose, 115. 
Miiller, A., ash in fibres, 438. 
Miiller, Hugo, analysis of cotton, 121. 

esparto, 131. 

flax, 124. 

jute, 125. 

hemp, 126. 

manila, 127. 

sunn hemp, 127. 

woods, 140. 
Multiple-effect evaporation, 166. 
Muriatic acid, 49. 

analysis, 355. 

density of solutions, 491. 

Naphthol, 326. 
Nascent state, 17. 
Negative pole, 455. 
Nemethy liquor apparatus, 220. 
New York Filter Co.'s filter, 341. 
New Zealand flax, 127. 
Nickel, and compounds of, 84. 
Nitrates, 31. 

analysis of, 395. 
Nitrate of iron, 397. 

of lead, 92. 

of potash, 64, 395. 

of silver, 96. 

of soda, 65, 396. 
Nitric acid, 30. 

analysis of, 356. 

density of solutions, 490. 
Nitrogen, 29. 

and carbon, 35. 

and chlorine, 55. 

and oxygen, 30. 

and sulphur, 48. 
Noble metals, 95. 
Nomenclature, 14. 
Nordhausen acid, 47. 
Normal paper, 420. 
Normal solutions, 352. 



512 



INDEX. 



Norton, Dr. L. M., moisture in pulp, 
451. 

Ochres, 400. 

Ohm, clef., 455. 

Ohm's law, 455. 

Oil of vitriol, 45. 

Oleo-resins, 138. 

Onyx, 58. 

Open-pan evaporation, 165. 

Orange mineral, 91, 399. 

Osmium, 100. 

Ovens, drying-, 448. 

Oxalic acid, analysis, 358. 

density of solutions, 483. 
Oxides, 26. 

of aluminum, 76. 

of antimony, 88. 

of arsenic, 60. 

of barium, 70. 

of cadmium, 75. 

of calcium, 71. 

of carbon, 32. 

of chlorine, 50. 

of cobalt, 83. 

of copper, 92. 

of chromium, 84. 

of indium, 94. 

of iron, 80. 

of lead, 91. 

of magnesium, 74. 

of manganese, 82. 

of mercury, 97. 

of molybdenum, 87. 

of nickel, 84. 

of nitrogen, 30. 

of potassium, 63. 

of silicon, 58. 

of silver, 95. 

of sodium, 360. 

of sulphur, 39. 

of tin, 85. 

of tungsten, 87. 

of vanadium, 90. 

of zinc, 74. 
Oxidizing flame, 34. 
Oxycellulose, 113. 
Oxygen, 25. 

mfg. of, 70. 

use in bleaching, 298. 
Oxyhydrogen flame, 28.' 
Ozone, 27. 

bleach, 298. 

Palladium, 99. 
Paper, ash in, 437. 

capillary power of blotting, 436. 

chlorides in, 437. 

classification of, 420. 

direction on machine, 421. 

dirt in, 423. 



Paper filler, det. of kind, 439. 

filter, analysis of, 287. 

finish of, 423. 

fracture length of, 425. 

free acid in, 437. 

ground wood in, 445. 

microscopical examination of, 441. 

normal, 420. 

parchment, 107. 

right and wrong sides, 421. 

starch in, 434. 

strength of, 424. 

stretch of, 424. 

testing, 420. 

thickness of, 424. 

water marks, 422. 
Paper birch, 147. 

mulberry, 128. 
Parchment paper, 107. 
Paris green, 60, 93. 
Paris, plaster of, 73. 
Partington lining, 234, 236. 

liquor apparatus, 215. 
Partition, use of porous, in electrolysis, 453. 
Paste, 92. 

Patents, list of sulphite, 471. 
Pearlash, analysis of, 373. 
Pearl hardening, 316, 439. 

analysis of, 383. 

composition of, 317. 
Pelouze, action of nitric acid on cellulose. 

108. 
Penta-nitro-cellulose, 110. 
Perchloric acid, 55. 
Permanganate of potash, 83. 
Peroxide of barium, 70. 

of hydrogen, 29. 

use as antichlor, 285. 
Pewter, 85. 

Phloroglucin, for paper-testing, 444, 445. 
Phosphate of lime, 73. 
Phosphate rock, 73. 
Phosphides, 59. 
Phosphor bronze, 60, 86. 
Phosphorus, 59. 
Photography, 96. 
Physical change, 3. 
Physical properties, 5. 
Picker seed, treatment of, 156. 
Picker waste, treatment of, 156. 
Pig iron, 81. 
Pine, gray, 142. 

white, 143. 
Plaster of Paris, 73. 
Platinum, 98. 
Plumbago, 31. 
Poles, def., 453. 

of dynamo, 455. 
Polythionic acids, 197. 
Poplar, 144. 
Porion evaporator, 172. 



INDEX. 



513 



Porter-Clark process, 335. 
Potash, 63. 
caustic, 64. 
•analysis, 361. 
density of solutions, 495. 
Potash alum, 77. 

density of solutions, 495. 
Potassium, 65. 

bichromate, 85, 398. 
carbonate, 64. 
chlorate, 54, 64. 
chloride, 64. 
chromate, 84. 
ferricyanide, 35. 
ferrocyanide, 35. 
hydrate, 64, 361, 495. 
hypochlorite, 296, 394. 
nitrate, 64, 395. 
oxide, 63, 361. 
permanganate, 83. 
tartrate, 64. 
Potential, 454. 

Prefixes, use in chemical terms, 465. 
Preparing wood, 188. 
Pronunciation of chemical terms, 465. 
Prussian blue, 35, 321, 400. 
Prussic acid, 35. 

Pulp, " air-dry," moisture in, 449. 
sampling, 447. 
testing for moisture, 446. 
Pulp, soda, 161. 

cause of had odors in, 38. 
effect of traces of black liquor, 289. 
yields, 149. 
sulphate, mfg., 178. 
sulphite, analysis of, bleached, 287. 
analysis of Mitscherlich, 267. 
analysis of quick cooked, 268. 
bleaching, loss in, 288. 
blue, addition of, to bleached, 285. 
burned, 266. 

cause of bad odors in, 38. 
chlorinated cellulose in, 286. 
dirt in, 267. 

fungoid growth on, 269. 
quality, conditions affecting, 261, 266. 
yellow discoloration on, 283. 
yields, 149, 269. 
Pumping sulphite liquor, 230. 
Pyrites, 37, 38. 
copper, 198. 
iron, 198. 
Pyrites burner, Freiberg, 198. 

Mitscherlich, 199. 
Pyrolusite, 82. 
Pyroxylin, 109. 

Quantity currents, 455. 
Quantivalence, 13. 
Quartz, 58. 
Quicklime, 71. 



Radicle, def., 69. 

Rags, boiling, etc., 151. 

Ramie, 127. 

Ramsay's bleach liquor, 295. 

Reactions, 17. 

analytical, 18. 

secondary, 453. 

synthetical, 18. 
Recovered lime, 175. 
Recovery of gas, 261. 

of soda, 158, 1C4. 
Red dyes, 325. 
Reducing flame, 34. 
Resins, 120, 138. 
Retention of fillers, 318, 440. 
Retort sulphur furnace, 193. 
Rhea, 128. 
Rhodium, 99. 
Ritter-Kellner filtering-tower, 200. 

lining, 237. 

tank apparatus, 211. 

tower system, 218. 
Rock crystal, 58. 
Rosin; 139. 

combined, det. of, 419. 

free, in size, 304. 
Rosin size, analysis of, 417. 

composition of, 305. 

preparation , 305. 

test for, 433. 
Rotary furnaces, 170. 

rag boilers, 151. 

sulphite digesters, 236. 
Rubbing test for paper, 431. 
Rubidium, 68. 
Ruby, 76. 

Ruby copper ore, 93. 
Russell cement lining, 247. 

lead lining, 235. 
Russian blast lamp, 351. 
Ruthenium, 99. 
Rutile, 86. 

Safranine, 326. 

Salomon-Briingger digester, 243. 
Salt cake, 385. 
Salt, common, 65. 

analysis of, 386. 

density of solutions, 482. 

electrolysis of, 453. 
Salt of tartar, 373. 
Saltpetre, 64. 

analysis of, 395. 
Salts, 15. 

Sampling pulp, 447. 
Sapphire, 76. 
Sapwood, 136. 
Scale, boiler, 333. 

preventives, 335. 
Scarlet liquor, 324. 
Schenck digester metal, 239. 



514 



INDEX. 



Schonbein, discovery of explosive cotton, 

108. 
Schopper paper-tester, 428. 
Schuman, det. of rosin size, 434. 
Schiinck, wax, etc., in raw cotton, 121. 
Schweitzer's reagent, 104. 
Sea-water, 49. 
Secondary reactions, 453. 
Seed-hairs, 121. 
Selenite, 73. 
Selenium, 48. 
Serpentine, 74. 
Sesquichloride of iron, 391. 
Sesquioxide of alumina, 77. 

of iron, 81. 
Silver, 95. 
Silver maple, 146. 
Silvering mirrors, 97. 
Silica, 58. 

in water, 334. 
Silicate of magnesia, 74. 

of soda, 58, 308. 
Silicon, 58. 
Sisal hemp, 129. 
Size, det. of in paper, 431. 
rosin, 304. 

action of light on, 306. 
analysis of, 417. 
composition of, 305, 306. 
prep, of, 305. 

with aluminate of soda, 307. 
with silicate of soda, 308. 
Sizing, 301. 

use of acid sulphites, 313. 
casein, 307. 
starch, 319. 
Smalt, 83. 
Soapstoue, 74. 
Soda, 65. 

analysis of, 367. 
density of solutions, 494. 
det. of in sulphite liquor, 416. 
recovery of, 158, 164. 
sources of loss in, 177. 
Soda alum, 77. • 
Soda, aluminate of, 307. 
Soda ash, 65. 

analysis of, 367. 
causticizing, 173-175. 
density of solutions, 494. 
Soda, caustic, 64. 
analysis of, 359. 
density of solutions, 493. 
Soda process for wood fibre, 161. 
boiling, 162. 
causticizing, 173.' 

Hewitt & Mond process, 175. 
recovery, 164. 
sources of loss, 177. 
Sodium, 64. 

by electrolysis, 453. 



Sodium aluminum fluoride, 77. 
biborate, 57, 65. 
bicarbonate, 65. 

analysis of, 371. 
bichromate, 398. 
carbonate, 65. 
analysis of, 367. 
density of solutions, 494. 
chloride, 65. 

analysis of, 386. 
density of solutions, 482. 
electrolysis of, 453-459. 
use in Hermite process, 459. 
hydrate, 64. 

analysis of, 359. 
density of solutions, 493. 
hypochlorite, 296, 394. 
hyposulphite, 44. 

use as antichlor, 283. 
nitrate, 65. 

analysis of, 396. 
silicate, 58. 

use in sizing, 308. 
sulphate, 385. 

sulphite, use as antichlor, 284. 
thiosulphate, 45. 

use as antichlor, 283. 
tungstate, 87. 
Soft water, 329. 
Solder, 86. 
Solids, mineral in water, 407. 

total in water, 406. 
Solutions, normal, 352. 
Solvay ash, use in sulphite process, 230. 
Solvay ijrocess, 68. 
Sorghum, 132. 
Specific gravity, 4. 

and degrees Beaume, 482, 483. 
and degrees Twaddle, 484. 
Specific heat, 7. 
Specular iron ore, 80. 
Speiss cobalt, 83. 
Spelling of chemical terms, 465. 
Sponges, fresh-water, 331. 
Spontaneous combustion, 26. 
Springer lining, 236. 
Spruce, 142. 

analysis of, 140. 
preparation, 188. 
specific gravity, etc., 138. 
yields, 149, 269. 
Spruce pulp, ground wood, 142. 
soda, 164. 
sulphate, 178. 
sulphite, 267. 

analyses of, 267, 268, 287. 
Stamp mill, 263. 
Standard papers, 442. 
Standard solutions, 352. 
Stannate of soda, 86. 
Starch, 319, 434. 



INDEX. 



515 



Steam, temperature of, 487. 

Steel, 81. 

Stibine, 88. 

Stochioinetry, 18. 

Stock in normal papers, 420. 

Storage tanks, 231. 

Storer, fixing of nitrogen by humus, 116. 

Straw, 129. 

treatment of, 158. 
Strontium, 71. 
Suberin, 141. 

Sublimation of sulphur, 197. 
Substantive colors, 320. 
Sugar of lead, 92. 

analysis of, 397. 

density of solutions, 494. 
Sulphates, 47. 

analysis of, 375. 
Sulphate of alumina, 77, 309. 

analysis of, 375. 

composition of, 310. 
Sulphate of ammonia, 69. 

of barium, 70. 

of calcium, 73, 228. 

of copper, 93, 384. 

of iron, 81, 385. 

of lead, 91, 233. 

of lime, 73. 

in ash of paper, 439. 

in sulphite liquor, 191, 221, 228. 

in towers, 207. 

in water, 334. 

paper-filler, 316. 

of magnesia, 74, 384. 

of soda, 65, 384. 

of zinc, 75, 384. 
Sulphate process, 178. 
Sulphides, 37. 
Sulphites, 41. 
Sulphite of lime, 43. 

antichlor, 284. 

cause of leaky tanks, 231. 

cause of leaky valves, 230. 

in liquor, 209. 

in Frank apparatus, 225. 

in Jung & Lindig lining, 245. 

in Salomon-BrLingger lining, 243. 

in sediment, 228. 

in towers, 207. 

incrustation in digester, 253. 
liquor apparatus, 229. 

precipitation of, 253. 

solubility, 191. 
Sulphite of magnesia, 43. 

in towers, 188. 
Sulphite of soda, 184. 

antichlor, 284. 
Sulphite liquors, analysis of, 412. 

composition of, 208, 209, 210, 226, 228*. 

preparation of, 190. 

absorption apparatus, 203. 



Sulphite liquors, lime for, 227. 
pumping, 230. 
storage, 231. 
sulphur burning, 192. 

waste, 270. 

action on life, 273, 274. 
Sulphite process, 179. 

boiling, 250. 

digesters and linings, 232. 

gas recovery, 261. 

history, 185. 

liquor-making, 190. 

patents, 471. 

preparing wood, 188. 

theory, 182. 

waste liquor, 270. 
Sulpho-arseuides, 60. 
Sulphur, 35. 

action of S0 2 on, 197. 

analyses of, 192. 

burning, 190, 192. 

filtering-tower, 201. 

flowers of, 36. 

grades; 37, 192. 

loss of, 228. 

sublimation, 197. 

yield of S0 2 , 225. 
Sulphur and carbon, 48. 

and chlorine, 55. 

and nitrogen, 48. 

and oxygen, 39. 
Sulphur, compounds of, 37. 
Sulphur dioxide, 40. 
Sulphuretted hydrogen, 39. 
Sulphuric acid, 45. 

action on lead, 233. 
on wood, 182. 

analysis of, 353. 

cause of loss of sulphur, 229. 

density of solutions, 488. 

det. of in sulphite liquor, 414. 

formation during boiling, 181, 185. 

during sulphur burning, 190, 191, 196, 
214. 

in alum, 311. 

prep, of different strengths, 489. 

removal from gas, 200, 203. 

use in bleaching, 292. 
in paper-testing, 443. 
Sulphuric anhydride, 47. 
Sulphurous acid, 40. 

action on life, 274. 
on sulphur, 197. 

available, 209. 

bleach, 44, 299. 

blowing off, 252. 

combined, 209. 

density of solutions, 498. 

determination of, 412. 

free, 209. 

gas pressure, 252. 



516 



INDEX. 



Sulphurous acid in burner gas, 208. 

in furnace gas, 190. 

in sulphite liquor, 210, 226, 228. 

in waste liquor, 273. 
use in pulp-making, 179. 
Sulphurous anhydride, 40. 
Sunn hemp, 127. 
Surface waters, 329. 
Sylvic acid, in resins, 139. 
Symbols, 10. 

graphic, 14. 
Synthetical reactions, 18. 
Sweet gum, 145. 

Talc, 74. 

Tamarack, 144. 

Tannic acid, test for animal size, 431. 

Tannin in bark, 141. 

Tappeiner, fermentation of cellulose, 115. 

Tartar emetic, 88. 

Tartar, salt of, analysis, 373. 

Tauss, effect of hot water on cellulose, 115. 

Tellurium, 48. 

Temperature, 6. 

effect on sizing, 312. 
Temporary hardness, 405. 
Terminations of chemical terms, 466. 
Tetranitro-cellulose, 110. 
Thallium, 92. 

Thermometers, relations between, 479. 
Thio-derivatives of cellulose, 468. 
Thionic acids, 47. 

Thiosulphate of calcium, use as antichlor, 
285. 

of soda, 45. 
Thiosulphuric acid, 45. 
Thorium, 87. 

Tilghman, inventor of sulphite process, 179. 
Tin, 85. 
Tinstone, 86. 
Titanium, 86. 
Trache'ids, 132. 

measurements of, 137. 
Trinitro-cellulose, 110. 
Tungsten, 87. 
Turpeth mineral, 97. 
Turquoise, 77. 
Twaddle's hydrometer, 484. 

Ulbricht, distribution of resin in wood, 139. 
Ultramarine, 321, 400. 
Unit of atomic weights, 8. 

of heat, 7, 33. 
Units, electrical, 454. 

of weights and measures, 478. 
Uranium, 85. 

Vanadium, 89. 

attraction of cellulose for compounds 
of, 104. 



Vanadium, attraction of oxycellulose for 

compounds of, 113. 
Vanillin, test for, 433. 

in waste liquors, 271. 
Varrentrapp's bleaching-salt, 295. 
Vegetable cell, 117. 
Venetian red, 399. 
Verdigris, 93. 
Vermilion, 97. 
Victoria green, 326. 
Vinegar, analysis of wood, 357. 
Violet dyes, 326. 
Vitriol, blue, 93, 384. 

green, 81, 385. 

white, 75, 384. 
Vitriol, oil of, 45. 

. analysis, 353. 

density of solutions, 488. 

prep, of different strengths, 489. 
Volt, def., 454. 
Volume, def., 4. 
Volumetric analysis, 353. 
Vomiting boiler, 157. 

Warren filters, 338. 

rotary furnace, 170. 
Washing and bleaching apparatus, Cloud- 
man, 290. 
Washing-soda, 65. 
Waste sulphite liquor, 270. 
Water, 29, 329. 

acid, 334. 

analysis, 403. 

Clark's softening process, 406. 

collecting samples, 346. 

color of, 330. 

effect upon bleaching, 290. 

for manufacturing purposes, 411. 

hardness of, 329, 333, 403. 

in wood, 137. 

organic and volatile matter in, 407. 

scale-forming, 333. 

sea, 49. 

total solids, 406. 

volume used per ton of paper, 330. 
Water-bath, 351. 

gas, 32. 

marks, 422. 
Water of ammonia, 69. 

analysis, 361. 
Waters, chalybeate, 81. 

surface and ground, 329. 
Wax in raw cotton, 121. 

in straw, 131. 
Weigelt-Reufach, action of waste liquors on 

life, 273. 
Weight, def., 4. 
Weights, atomic, 8. 

metric system, 478. 
Well-thread, 332. 
Wendler paper-tester, 425. 



INDEX. 



517 



Wendler-Spiro liquor apparatus, 221. 
Wenzel cement lining, 246. 
Wheelwright cooler, 203. 

digester, 238. 

liquor apparatus, 215. 
White arsenic, 60. 

hirch, 147. 

fir, 143. 

lead, 91. 

pine, 143. 
Whiting, 374. 

Wiesner, starch in ancient papers, 319. 
Willesden paper, 105. 
Willow, 148. 

Wilson's bleach liquor, 295. 
Witherite, 70. 

Witz, action of oxidizing agents on cellu- 
lose, 113. 
Wood, 132. 

density of, 137. 

elements of, 133. 

growth of, 135. 

heaviest, 138. 



Wood, moisture in, 137. 

of coniferous trees, 134. 

preparing, 161, 188. 

resin in, 139. 
Wood-cells, air and water in, 137. 
Wood-fibres, 133. 
Wood-vinegar, 357. 
Woods, analyses of, 140. 

fuel value, 138. 
Woods used in pulp-making, 141, 149, 150. 
Wiirster, determination of starch, 434. 

theory of sizing, 304, 433. 

Yaryan evaporator, 166. 
Yellow dyes, 326. 
Yttrium, 79. 

Zinc, 74. 

bleach liquor, 295. 

compounds of, 74, 75. 

sulphate, analysis of, 384. 
Zirconium, 86. 
Zylonite, 111. 



NMTRONH POROUS MLUM 



FOR PAPER MAKERS' USE. 



THE Original "Porous" Alum and the only Alum made from 
KRYOLITH ALUMINA. Do not be deceived by parties offer- 
ing so-called Porous, but buy and take no other than Natrona 
Porous Alum. 



Penna. Salt yviFe. 0©., 

sole manufacturers, 
1 15 Chestnut St., Philadelphia, Fa. 

THE READY FAMILY SOAP MAKER. 




LEWIS' 98% LYE 

Powde:^ed and Perfumed 

( PATENTED). 

The strongest and purest Lye made. Will make the best Per- 
fumed Hard Soap in twenty minutes without boiling. 

The best water softener made. The best disinfectant. 

SOME OF THE ADVANTAGES OBTAINED BY USING LEWIS' 
98 PER CENT. POWDERED LYE ARE : 

Unlike other Lye, it is packed in an iron can with a removable 
lid, easily taken oft, thereby saving trouble and danger (from fly- 
ing particles). It being a fine powder, and the lid easily removed, 
the contents are always ready for use. A teaspoonful can be used, 
in scrubbing, etc., and the lid replaced, saving the balance. "With 
other Lyes all must be used quickly, or the strength is gone. 
Absolute purity. The best soap can be made in from ten to twenty 
minutes with this Lye. In making soap no failure is possible if the 
pimple directions are followed One can is equal to iO pounds of 
Washing Scda ; is 28 per cent, stronger, and will saponify one 
pound moie grease than any other preparation. One teaspocnful 
will thoroughly cleanse waste pipes, sinks, drains or closets, and 
is invaluable for killing insects, etc. 



PENNA. SALT MFG. CO., 



General Agents, 
PHILADELPHIA, PA. 



THE HELLER k MERZ 



PROPRIETORS OF THE 



American Ultramarine .# Globe Aniline Works, 

55 MAIDEN LANE, 

p. o. box 1094, New York. 




WORKS, NEWARK, N. J. 



Ultramarine for Paper Makers, 

R. C. No. 4. R. S. xx. A. P. R. x. 



ANILINE COLORS 



OF ALL SHADES. 



SAMPLES MATCHED, 



-KH- 



SAMPLES MATCHED. 

This Sheet Made and Colored in Our Laboratory. 

[over]. 



IE HELLER k MERZ CO 



NEW YORK, 



MANUFACTURERS AND IMPORTERS OF 

Ultramarine Blues 



AND 



Aniline Colors. 

SAMPLES FOR ALL INDUSTRIES 
CAREFULLY MATCHED. 



ULTRAMARINE FOR PAPER MAKERS. 



BROMO FLUORESCEIN, 

ROSE BENGALE, 

PHLOXINES, 

ERYTHROSINES, 

SAFROSINE, 

EOSINES, 

MAGENTAS, 

GARNETS, 



VIOLETS, 
ANILINE BLUES, 
NIGROSINES, 
ORANGE, CARMOSINES, 
SCARLETS, 
BISMARCK BROWNS, 
NANKING BROWNS, 
CHRYSOIDINES, Etc. 



(VVAVAVvNWAVAVA 



P. O. BOX 1094, works: 

NEW YORK. NEWARK, N. J, 

fOVEB.] 



V V V 



^TATHIESON 

ALKALI WORKS, 

SALTYILLE, YA. 

58 Per Cent. PURE ALKALI, 

CAUSTIC SODA, All Strengths, 

BLEACHING POWDERS. 
SULPHATE OF SODA for Glass Makers. 




HE unexcelled quality of merchandise turned out by 
Messrs. N. Mathieson & Co., of Widnes, is well known 
among all consumers in the United States, Mathieson's 
Bleaching - Powders especially commanding' the highest price of 
any offered on this market for many years. Alkali and Caustic 
Soda as well, bearing Mr. Mathieson's name, have earned a repu- 
tation excelled by no other large maker. Mr. Mathieson is a large 
stockholder in this company, and Mr. T. T. Mathieson, for many 
years past having sole supervision of N. Mathieson & Co.'s Works 
in England, has entire charge of the Mathieson Alkali Works in 
this country. 

These Works are rapidly approaching completion, and goods 
will be in the market within a few months. 
Correspondence solicited by 

MASON, CHAPIN & CO., 

PROVIDENCE, NEW YORK, BOSTON 



A. D. LITTLK, 



(GRIFFIN & LITTLE) 



Consulting and Analytical 
Chemist, 



EXPERT IN PATENT CAUSES, 



103 Milk Street, Boston 



Particular attention given to all Chemical Matters pertaining to the 

Treatment of Fibres and the Manufacture of Pulp and Paper. 

Chemical and Microscopical Analyses of Paper and 

Paper-Making Materials. Commercial 

Analyses of every description. 



New Processes Investigated and Developed. 



XA-lUm of all kinds for every possible 
purpose of the paper-maker. 

PaSte YelloW of fine Canary 
Tint ; stands calender heat without change. 

JTclSte JtvOSe stands alum, acids, 
alkali, calenders and sunlight. COSTLY, 
but the only permanent and delicate rose 
tint known. 

Jr clSte lJlLie, perfectly even in tint- 
ing strength and absolutely uniform. 

1 3,1 II IS, the best it is possible to manu- 
facture for house, mill or machinery. 

HARRISON BROS. & CO., 
Philadelphia, 
New York, 
Cincinnati. 



ALUM! 



♦ ♦ ♦ ♦ 



Bleaching, Sizing and 
Filtering Alums 

Made Expressly for 
Paper Makers' Use. 

Those requiring a strictly neu- 
tral and pure Alum for the 
highest grades of paper should 
try the 

MERRIMAC POROUS ALUM 

(either lump or ground, as pre- 
ferred). Samples and prices of 
the different grades sent on 
application. Our works being 
on the Boston and Maine Rail- 
road system, we are well situ- 
ated for reaching all parts of 
New England. 



Merrimac 

Chemical Co., 

13 Pearl Street, 

Boston, Mass. 



[COPY.] 

Office of State Assayer. ( 
BOSTON, June 30, 1894. | 
We have examined a number of samples of 
the Merrimac Porous alum, and have found 
this Alum to be of excellent quality both in 
respect to purity and strength, and suitable for 
the highest grades of paper. 

(Signed) Griffin & Little. 



The United Alkali Co., Ltd., 

OF GREAT BRITAIN, 

Head Office, Exchange Buildings, LIVERPOOL, ENGLAND. 

Taid tip Capital, - - $42,000,000. 
Undivided Surplus, - - 2,500,000. 



MANUFACTURERS OF 



n/^r\ a a qti (All strengths, by Ammonia and Le Blanc 
uUUrt rtOn Processes, Carbonated and Caustic), 

CAUSTIC SODA, 

(All strengths from 60 per cent, to Double Refined 98 per cent.), 



Slow and 



HIGH TEST BLEACHING POWDER, Ql 
PEARL HARDENING, 

SULPHATE OF ALUMINA 

(Special quality free from Iron) 

J. L.&D.S. RIKER, 

Importers and Manufacturers' Agents, 

45 Cedar Street, NEW YORK, 

SOLE AGENTS FOR THE UNITED STATES AND CANADA OF 

THE UNITED ALKALI CO.,™*, 

OF GREAT BRITAIN, 

For the sale of their various brands of Bleaching 
Towder and other articles of their manufacture. 



THE SOLYAY PROCESS CO., 

SYRACUSE, N. V. 
Works at GEDDES, N, Y,, three miles West of Syracuse, 



r 58 per cent, actual Alkali, equals 99.16" 
PURE SODA. . . •. -j per cent. Carbonate Soda ; of uniform 

( strength and purity. 

f 48 per cent, actual Alkali, specially 
AMMONIA SODA. -J prepared for the glass trade ; stronger 

( than the so-called 48 per cent. Soda Ash. 

BICARBONATE ( The basis of Baking Powders, Ro- 

SODA. ( chelle Salts. and carbonated beverages. 

r In all usual strengths for making Pa- 
CAUSTIC SODA. . 1 per, Soap, Oil, Glycerine, Sugar, Starch, 

( Etc. 

CRYSTAL ( Superior to the Pearl hardening in 

PAPER FILLER. ( common use for surfacing paper stock. 

HYDRATE ( ^ su P er i° r basis for making Alum 

< and Salts of Alumina and other mor- 

OF ALUMINA. ( dants. 

OXJDJ5 OF ( Refined from Bauxite, 98 per cent. 

•< pure ; well suited for making pure 
ALUMINA. ( Aluminum and its alloys. 



Aggregate Finished Product, 500 Tons Daily. 



NEW YORK SELLING AGENTS : 

WING & EVANS, 

54 William St., New York City. 



Paper Makers 



ALUMS 



For Sizing, 



Bleaching and 



Filtering Purposes. 



WRITE FOR SAMPLES AND PRICES. 



Martin Kalbfleisch Chemical Co. 



55 FULTON ST., NEW YORK. 



A. KLIPSTEIN & COMPANY, 

122 Pearl St., New York. 

134 Milk St., Boston. 124 Michigan St., Chicago. 

120 Arch St., Philadelphia. Hamilton, Ont. 

ALL CHEMICALS AND DYES 

Used by Paper Makers. 

SODA ASH 58% (Ammonia Soda), 

CAUSTIC SODA, 
ALUM, SULPHATE OF ALUMINA, 
BLEACHING POWDER 

(English. German and French). 

ANILINE COLORS 

including the specialties of the Soc. Chem. ind., Basel. 

AURAMINE, 

RHODAMIIME, 

VICTORIA BLUE, 
EOSIIME. 

Paper Blues, Ultramarine Blue. Prussian Blues. 



